We give the following examples:—

Pinus Grandis (Dougl.), in New California, attains a height of 202–224

feet.

Pinus Frémontiana (Endl.), also there, and probably of the same

height.[PK]

Dacrydium Cupressinum (Solander), in New Zealand, above 213 feet.

Pinus Lambertiana (Dougl.), in North-western America, 223–234 feet.

Araucaria Excelsa (R. Brown), the Cupressus columnaris of Forster, in

Norfolk Island and the surrounding rocks, 182–223 feet. The six

Araucariæ hitherto known fall into two groups, according to Endlicher:

α. The American (Brazil and Chili), A. brasiliensis [Rich.], between

15° and 25° south lat., and A. imbricata [Pavon], between 35° and 50°

south lat.; the latter 234–260 feet;

β. The Australian (A. Bidwilli [Hook.] and A. Cunninghami [Ait.] on

the eastern side of New Holland, A. excelsa of Norfolk Island, and A.

Cookii [R. Brown] of New Caledonia). Corda, Presl, Göppert, and

Endlicher have already found five fossil Araucariæ in lias, in chalk,

and in lignite.[PL]

Pinus Douglasii (Sab.) in the valleys of the Rocky Mountains and at

the Columbia River (north lat. 43°–52°). That meritorious Scotch

botanist, whose name this tree bears, suffered a dreadful death in

1833, when he came from New California to collect plants on the

Sandwich Islands. He inadvertently fell into a pit, into which one of

the wild bulls of that country, always viciously disposed, had

previously fallen. This traveller has described from accurate

measurements a stem of P. Douglasii, which at three feet from the

ground was 57½ feet round, and 245 feet high.[PM]

Pinus Trigona (Rafinesque), on the western slope of the Rocky

Mountains.[PN] This “gigantic fir” was measured with great care; the

girth of the stem at 6¼ feet above the ground was often from 38 to 45

feet. One stem was 300 feet high, and without branches for the first

192 feet.

Pinus Strobus (in the eastern part of the United States of North

America, especially on this side of the Mississippi, but also again in

the Rocky Mountains, from the source of the Columbia to Mount Hood,

from 43° to 54° north lat.), in Europe called the Weymouth Pine, and

in North America the White Pine, commonly no more than 160 to 190 feet

high, but several have been seen in New Hampshire of 250 and 266

feet.[PO]

Sequoia Gigantea (Endl.; the Condylocarpus, Sal.), of New California,

like the Pinus trigona, about 300 feet high.

The nature of the soil and the conditions of heat and moisture, on

which the nourishment of plants simultaneously depends, promote, it

must be admitted, the development and the increase of the number of

the individuals in a species; but the gigantic height attained by the

stems of a few among the many nearly allied species of the same genus

is not dependent on soil and climate but on a specific organization,

on internal natural disposition, common alike to the vegetable and to

the animal world. With the Araucaria imbricata of Chili, the Pinus

Douglasii of the Columbia River, and the Sequoia gigantea of New

California (245–300 feet) contrasts most strongly—not the Willow

(_Salix arctica_) stunted by cold or mountain height, and only two

inches high,—but a little phanerogamic plant in the beautiful climate

of the southern tropical region, in the Brazilian province of Goyaz.

The moss-like Tristicha hypnoides, of the Monocotyledonous family of

the Podostemeæ, hardly attains the height of three lines. “While

crossing the Rio Clairo in the province of Goyaz,” says an excellent

observer, “I perceived on a stone a plant, the stalk of which was not

more than three lines high, and which I considered at first to be a

moss. It was, however, a phanerogamic plant, supplied with sexual

organs like our oaks, and those gigantic trees which raised their

majestic heads around.”[PP]

Besides the height of the stem, the length, breadth, and position also

of the leaves and fruit, the aspiring or horizontal, almost umbellate

ramification, the gradation of the colour from fresh or silver-greyish

green to dark brown, give a peculiar physiognomical character to the

Coniferæ. The acicular leaves of Pinus Lambertiana (Douglas) in

North-Western America are five, those of the P. excelsa (Wallich) on

the southern slope of the Himalaya near Katmandu, seven, and those of

P. longifolia (Roxb.) on the mountain range of Cashmere, more than

twelve inches long. Moreover, in one and the very same species, these

acicular leaves vary in the most remarkable manner, from the combined

influence of the nourishment derived from soil and air, and of the

height above the level of the sea. I found these variations in the

length of the leaves of our common wild pine (_Pinus sylvestris_) so

great, while travelling in a west and east direction over an extent of

80° of longitude (more than 3040 miles) from the Scheldt, through

Europe and Northern Asia, to Bogoslowsk, in the Northern Ural, and

Barnaul beyond the Obi, that occasionally, deceived by the shortness

and rigidity of the leaves, I have mistaken it for another species of

pine, allied to the mountain fir, _P. rotundata_, Link, (_Pinus

uncinata_, Ram.) These are, as Link correctly observes,[PQ]

transitions to Ledebour’s P. sibirica of the Altai.

The delicate and pleasing green though deciduous foliage of the

Ahuahuete (_Taxodium distichum_, Rich., _Cupressus disticha_, Linn.)

on the Mexican plateau especially delighted me. In this tropical

region the tree, swelling out to a portly bulk, and the Aztec name of

which signifies “water-drum” (from atl, water, and huehuetl, drum),

flourishes from 5750 to 7670 above the level of the sea, whilst it

descends towards the plain in the marshy district (Cypress swamps) of

Louisiana as far as 43° lat. In the southern States of North America

the Taxodium distichum (_Cyprès chauve_), as well as in the lofty

plains of Mexico, attains a height of 128 feet, with an enormous

girth, the diameter being from 30 to nearly 40 feet, when measured

near the ground.[PR] The roots, too, present a very remarkable

phenomenon, for they have woody excrescences, which are sometimes of a

conical and rounded, sometimes of a tabular shape, and project three

and even nearly five feet above the ground. Travellers have compared

these woody excrescences, in spots where they are numerous and

frequent, to the grave-tablets of a Jewish churchyard. Auguste de St.

Hilaire remarks, with much acuteness: “These excrescences of the bald

cypress, which resemble boundary-posts, may be regarded as exostoses,

and like these live in the air; adventitious buds would doubtless

escape from them, if the nature of the tissue of the coniferous plants

did not oppose itself to the development of those concealed germs that

give birth to these kinds of buds.”[PS] In addition to the above, a

remarkably enduring vitality is manifested in the roots of

cone-bearing trees by the phenomenon which, under the name of

“Effervescence,” (aftergrowth?) has attracted, in many ways, the

attention of botanical physiologists, and which phenomenon, it

appears, rarely displays itself in other dicotyledonous plants. The

stumps of the felled white Pine, left in the ground, form, during a

succession of several years, new layers of wood, and continue to

increase in thickness, without throwing out shoots, branches, or

leaves. The excellent observer Göppert believes, that this takes place

solely through nourishment derived from the roots, which the extremity

of the stem receives from a neighbouring living tree of the same

species. The roots of the living tree he conceives are organically

incorporated with those of the stump.[PT] Kunth, in his excellent new

_Lehrbuch der Botanik_, is opposed to this explanation of a

phenomenon, which was even known, though imperfectly, to

Theophrastus.[PU] According to him, this process is perfectly

analogous to that by which metallic plates, nails, carved letters,

nay, even stags’ horns become imbedded within the body of wood. “The

cambium, that is, the thin, walled cellular tissue, conducting

muco-granular sap, from which new formations alone proceed, continues

without any relation to the buds (being perfectly independent of them)

to deposit new layers of wood on the outermost layer.”[PV]

The relation above alluded to, between the absolute height of the

ground and the geographical as well as isothermal latitude, shows

itself often, no doubt, when one compares the arborescent vegetation

of the tropical part of the Andes chain with the vegetation of the

north-west coast of America, or the banks of the Canadian lakes. The

same remark was made by Darwin and Claude Gay in the southern

hemisphere, when they, in their descent from the plateau of Chili,

advanced towards Eastern Patagonia, and the Archipelago of Tierra del

Fuego; here woods of Drymis Winteri, together with Fagus antarctica

and Fagus Forsteri, cover every thing with long uniform rows in a

northern and southern direction down to the low lands. Trifling

deviations from the law of constant _station-ratios_ between _mountain

height_ and _geographical latitude_, depending or local causes, not

sufficiently investigated, occur even in Europe. I would call to mind

the limits of altitude for the birch and common fir in a part of the

Swiss Alps, on the Grimsel. The fir (_Pinus sylvestris_) flourishes

there up to 6330; and the birch (_Betula alba_) up to 6906 feet;

beyond them again there is a belt of stone pines (_Pinus cembra_),

whose upper boundary is 7343 feet. The birch, in consequence, lies

there between two belts of Coniferæ. According to the excellent

observations of Leopold von Buch, and the more recent ones of Martius,

who also visited Spitzbergen, the limits of the geographical

distribution in the high Scandinavian north (in Lapland) are as

follows: “The Fir extends to 70°; the White Birch (_Betula alba_) to

70° 40′; the Dwarf-Birch (_B. nana_) to 71° at least: Pinus cembra is

entirely wanting in Lapland.”[PW]

As the length and the position of the acicular leaves define the

physiognomic character of the coniferæ, this is still more designated

by the specific difference of the leaf-breadth, and the parenchymatous

development of the appendicular organs. Several species of Ephedra may

be said to be almost leafless; but in Taxus, Araucaria, Dammara,

(Agathis), and the Salisburia adiantifolia of Smith (_Gingko biloba_,

Linn.), the breadth of the leaf gradually increases. I have here

arranged the genera morphologically. Even the names of the species, as

first chosen by botanists, indicate such an arrangement. Dammara

orientalis of Borneo and Java, often 11 feet in diameter, was at first

named loranthifolia: Dammara australis (Lamb.), in New Zealand, rising

to 150 feet high, was originally named zamæfolia. Neither of these has

acicular leaves, but “folia alterna oblongo lanceolata, opposita, in

arbore adultiori sæpe alterna, enervia, striata.” The lower surface of

the leaf is densely covered with stomata. These transitions of the

appendicular system, from the greatest contraction to a broad leaf

surface, possess, like every advance from simple to compound, both a

morphological and a physiognomical interest.[PX] The short-stalked,

broad, split leaf of the Salisburia (Kämpfer’s Ginkgo), has also the

breathing pores (stomata) only on the inferior side. The original

habitat of the tree is not known. It became distributed from the

Chinese temples to the gardens of Japan, in consequence of the

intercourse that existed in olden times between the congregations of

Buddha.

I was a witness of the singularly painful impression, which the first

sight of a pine-forest at Chilpanzingo made on one of our companions

in travelling from a port in the South Sea through Mexico to Europe.

Born in Quito, under the equator, he had never seen needle-leaved

trees and folia acerosa. The trees appeared to him to be leafless, and

because we were journeying towards the cold north, he thought he

recognised already, in the extreme contraction of the organs, the

impoverishing influence of the Pole. The traveller, whose impressions

I am here describing, and whose name neither Bonpland nor myself can

mention without regret, was an excellent young man, the son of the

Marquis de Selvalegre, Don Carlos Montufar, whose noble and ardent

love of freedom courageously led him, a few years later, to a violent,

though not dishonourable, death, in the war of independence, waged by

the Spanish colonies.

Footnote 94:

p. 227—“_Pothos plants, Aroideæ_.”

Caladium and Pothos are forms appertaining exclusively to the tropical

world, whilst the different species of Arum belong more to the

temperate zone. Arum italicum, A. dracunculus, and A. tenuifolium

advance as far as Istria and Friuli. No Pothos has hitherto been

discovered in Africa. The East Indies possess several species of this

genus (P. scandens and P. pinnata), which have a less beautiful

physiognomy and are of less luxuriant growth than the American Pothos

plants. We discovered a beautiful true arborescent Aroidea (Caladium

arboreum), having a stem from 16 to more than 21 feet in height, near

the convent of Caripe, east of Cumana. Beauvois found a singular

Caladium (Culcasia scandens) in the kingdom of Benin.[PY] In the

Pothos form the parenchyma occasionally expands to so great a degree

that the leaf-surface becomes perforated with holes, as in Calla

pertusa (Kunth), and Dracontium pertusum (Jacquin), which we collected

in the forests of Cumana. It was the Aroideas which first drew

attention to the remarkable phenomenon of the _fever-heat_ evolved by

certain plants during the period of their inflorescence, and which

even sensibly affects the thermometer, and is connected with a great

and temporary increase in the absorption of oxygen from the

atmosphere. Lamarck, in 1789, observed this increase of temperature in

the Arum italicum. According to Hubert and Bory de St. Vincent, the

vital heat of the Arum cordifolium rises in the Isle of France to 110°

or 120°, whilst the temperature of the surrounding air is only 66°.2

Fahr. Even in Europe, Becquerel and Breschet found a difference of

39°.4. Dutrochet observed a paroxysm,—a rhythmical decrease and

increase of vital heat,—which appeared by day to attain a double

maximum. Théodore de Saussure remarked analogous augmentations of

heat, although only of 1°.1 and 1°.8 Fahr., in other families of

plants; as, for instance, in Bignonia radicans and Cucurbita pepo. In

the latter, the male plant exhibited a greater increase of temperature

than the female, when measured by a very sensitive thermoscopic

apparatus. Dutrochet—whose early death is greatly to be regretted, on

account of the important services he rendered to physics and vegetable

physiology—likewise observed,[PZ] by means of thermo-magnetic

multiplicators, a vital heat of 0°.25 to 0°.67 Fahr. in many young

plants (Euphorbia lathyris, Lilium candidum, Papaver somniferum), and

even among funguses, in many species of Agaricus and Lycoperdon. This

vital heat disappeared at night, but not by day, even when the plants

were placed in the dark.

The contrast presented by the physiognomy of the Casuarineas,

acicular-leaved trees, and the almost leafless Peruvian Colletias and

Pothos plants (Aroideas), is still more striking when we compare these

types of extreme contraction in the leaf form with Nymphæaceæ and

Nelumboneæ. Here we again meet, as in the Aroideæ, with leaves in

which the cellular tissue is excessively expanded upon long, fleshy,

succulent petioles,—as Nymphæa alba, N. lutea, N. thermalis (formerly

called N. lotus, from the hot spring of Pecze, near Groswardein in

Hungary), the species of Nelumbo, Euryale amazonica (Pöppig), and

Victoria Regina, allied to the prickly Euryale, although of a very

different genus, according to Lindley, and discovered in 1837 by Sir

Robert Schomburgk in the river Berbice, in British Guiana. The round

leaves of this splendid aquatic plant are from 5 to 6 feet in

diameter, and surrounded by upright margins from 3 to 5 inches in

height, which are light green on the inner side, but of a bright

crimson on the outside. These agreeably perfumed flowers, of which 20

or 30 may be seen together in a small space, are about 15 inches in

diameter, of a white or rose colour, and have many hundred petals.[QA]

Pöppig also gives to the leaves of his Euryale amazonica, which he

found at Tefé, a diameter of about 6 feet.[QB] Whilst Euryale and

Victoria present a greater parenchymatous expansion of the leaf-form

in all its dimensions than other genera, the most gigantic development

of the blossoms occurs in a parasitical Cytinea, which Dr. Arnold

discovered in Sumatra in 1818. This flower, Rafflesia Arnoldi (R.

Brown), has a stemless blossom measuring three feet in diameter,

surrounded by large leaf-like scales. Like funguses, it has an animal

odour, and smells something like beef.

Footnote 95:

p. 227—“_Lianes, Creeping Plants, (Span. Vejuccos.)_”

According to Kunth’s division of Bauhinias, the true genus Bauhinia

belongs to the New Continent. The African Bauhinia, B. rufescens

(Lam.), is a Pauletia (Cav.), a genus of which we also discovered some

new species in South America. In the same manner the Banisterias of

the Malpighiaceæ are actually an American form. Two species are

indigenous to the East Indies, and one—described by Cavanilles as B.

leona—to Western Africa. In the tropical zone, and in the Southern

hemisphere, species of the most different families belong to the

climbing plants which in those regions render the forests so

impenetrable to man and so accessible and habitable to the whole

monkey family (Quadrumana), the Cercoleptes, and the small tiger cats.

The Lianes thus afford whole flocks of gregarious animals an easy

means of rapidly ascending high trees, passing from one tree to

another, and even of crossing brooks and rivulets.

In the south of Europe and in the north of America, Hops from the

Urticeæ, and the species of Vitis from the Ampelideæ, belong to

Climbing Plants; while this form is represented in the tropics by

climbing and trailing grasses. We found on the elevated plains of

Bogota, in the pass of Quindiu in the Andes, and in the Cinchona

forests of Loxa, a Bambusa allied to Nastus, our Chusquea scandens,

twined round powerful trunks of trees, adorned at the same time with

flowering Orchideæ. Bambusa scandens (Tjankorreh), which Blume found

in Java, belongs probably to Nastus, or to the grass-genus Chusquea,

the Carrizo of the Spanish settlers. In the pine forests of Mexico,

Climbing Plants seem to be entirely wanting; but in New Zealand a

fragrant Pandanus, Freycinetia Banksii, together with one of the

Smilaceæ, Ripogonum parviflorum (R. Brown), which renders the forests

almost impenetrable, winds round a gigantic fir-tree more than 200

feet high, Podocarpus dacryoides (Rich.), called Kakikatea in the

language of the country.[QC]

A striking contrast to these Climbing Grasses and Creeping Pandaneas

is afforded by the splendid many-coloured blossoms of the Passion

flowers (among which, however, we ourselves found one arborescent,

upright, species (Passiflora glauca) in the Andes of Popayan, at an

elevation of nearly 10,500 feet, and by the Bignoniaceæ, Mutisiæ,

Alströmeriæ, Urvilleæ, and Aristolochiæ. Among the latter, our

Aristolochia cordata has a coloured (purplish red) calyx, about

seventeen inches in diameter; “flores gigantei, pueris mitræ instar

inservientes.” Owing to the quadrangular form of their stalks, their

flattening, which is not occasioned by any external pressure, and a

band-like undulatory motion, many of these climbing plants have a

peculiar physiognomy. The diagonal intersections of the stems of

Bignonias and Banisterias form, by means of furrows in the ligneous

substance, and through its clefts, where the bark penetrates to some

depth, cruciform or mosaic-like figures.[QD]

Footnote 96:

p. 228—“_The form of Aloes_.”

To this group of plants, which is characterised by a great similarity,

belong Yucca aloifolia, which penetrates as far north as Florida and

South Carolina; Y. angustifolia (Nutt.), which advances to the banks

of the Missouri; Aletris arborea; the Dragon-tree of the Canaries, and

two other Dracænas belonging to New Zealand; arborescent Euphorbias;

and Aloe dichotoma, Linn., (formerly the genus Rhipidodendrum of

Willdenow), the celebrated Koker-boom, whose stem is four feet in

thickness, about twenty feet high, and has a crown measuring 426 feet

round.[QE] The forms which I have here associated together belong to

very different families: as, for instance, to the Liliaceæ,

Asphodeleæ, Pandaneæ, Amaryllideæ, and Euphorbiaceæ; and are

therefore, with the exception of the last named, all included under

the great division of Monocotyledons. One of the Pandaneæ, Phytelephas

macrocarpa (Ruiz), which we found on the banks of the Magdalena river

in New Granada, exactly resembles with its feathery leaves a small

palm-tree. The Tagua (as it is called by the Indians) is moreover, as

Kunth has observed, the only Pandanea of the New Continent. The

singular Agave-like and high-stemmed Doryanthes excelsa of New South

Wales, which the intelligent Correa de Serra was the first to

describe, belongs to the Amaryllideæ, like our low-growing Narcissuses

and Jonquils.

In the candelabra-like form of Aloes, the branches of the main-trunk

must not be confounded with the flower-stalks. In the American aloe,

Agave Americana (Maguey de Cocuyza), which is entirely wanting in

Chili, and in the Yucca acaulis (Maguey de Cocuyza), the leaf-stalks

present a candelabra-like arrangement of the blossoms during the

excessively rapid and gigantic development of the inflorescence,

which, as is well known, is but too transient a phenomenon. In some

arborescent Euphorbias the physiognomical character depends, however,

on the branches and their arrangement. Lichtenstein describes,[QF]

with much animation, the impression made upon him by the appearance of

an Euphorbia officinarum which he saw in the “Chamtoos Rivier,” near

Cape Town. The form of the tree was so symmetrical, that it repeated

itself on a small scale, like a candelabrum, to a height of more than

30 feet. All the branches were furnished with sharp thorns.

Palms, Yucca and Aloe plants, arborescent Ferns, some Aralias, and the

Theophrasta, where I have seen it in a state of luxuriant growth,

present to the eye a certain physiognomical resemblance of character

by the nakedness of the stems (there being no branches) and the beauty

of their summits or crowns, however they may otherwise differ in the

structure of the inflorescence.

Melanoselinum decipiens, (Hofm.), which has been introduced into our

gardens from Madeira, and is sometimes from 10 to 12 feet high,

belongs to a peculiar group of arborescent umbelliferæ allied to the

Araliaceæ, to which other species, as yet undiscovered, will

undoubtedly at some future time be added. Ferula, Heracleum, and

Thapsia likewise attain a considerable height, but they are still

herbaceous shrubs. Melanoselinum stands almost entirely alone as an

arborescent umbelliferous plant; Bupleurum (_Tenoria_) fruticosum,

Linn., of the shores of the Mediterranean, Bubon galbanum of the Cape,

and Crithmum maritimum of our sea-coasts, are only shrubs. Tropical

countries, where, as Adanson long since very correctly remarked,

Umbellifereæ and Crucifereæ are almost wholly wanting in the plains,

exhibit, as we ourselves observed, the most dwarfish of all the

umbelliferous family on the lofty mountain ridges of the South

American and Mexican Andes. Among the thirty-eight species which we

collected on elevations whose mean temperature was below 54°.5 Fahr.,

we found Myrrhis andicola, Fragosa arctioïdes, and Pectophytum

pedunculare, interspersed with an equally dwarfish Alpine Draba,

growing moss-like close to the rock and the frequently frozen earth,

at a height of 13,428 feet above the level of the sea. The only

tropical umbelliferous plants which we found on the plain in the New

Continent were two species of Hydrocotyle (_H. umbellata_ and _H.

leptostachya_) between the Havannah and Batabano, and therefore at the

extreme limit of the torrid zone.

Footnote 97:

p. 228—“_The form of Grasses_.”

The group of the arborescent grasses which Kunth has collected under

the head of Bambusaceæ, in his great work on the plants collected by

Bonpland and myself, constitutes one of the most beautiful adornments

of tropical vegetation. Bambu, called also Mambu, occurs in the Malay

language, although according to Buschmann merely as an isolated

expression, the ordinary term in use being buluh, whilst the only name

for this species of cane in Java and Madagascar is wuluh, voulou. The

numbers of the genera and species included in this group have been

extraordinarily increased by the industry of botanical travellers. It

has been found that the genus Bambusa is entirely wanting in the New

Continent, to which region, however, the gigantic Guaduas, discovered

by us, and which attain a height of from 50 to 64 feet, together with

the Chusquea, exclusively belong; that Arundinaria (Rich.) occurs in

both continents, although differing specifically in each; that Bambusa

and Beesha (Rheed.), occur in India and the Indian Archipelago; and

that Nastus grows in the islands of Madagascar and Bourbon. With the

exception of the high-climbing Chusquea, these forms morphologically

replace each other in different parts of the earth. In the northern

hemisphere far beyond the limits of the torrid region, in the valley

of the Mississippi, the traveller is gladdened by the sight of a

species of Bamboo, the Arundinaria macrosperma, formerly called also

Miegia and Ludolfia. In the southern hemisphere, in the south of

Chili, between the parallels of 37° and 42°, Gay found one of the

Bambusaceæ more than 20 feet high (not a climbing, but a still

undescribed arborescent self-supporting Chusquea), growing, mingled

with Drymis Chilensis, in a region clothed with an uniform

forest-covering of Fagus obliqua.

Whilst in India the Bambusa flowers so frequently that in Mysore and

Orissa the seeds are mixed with honey, and eaten like rice,[QG] in

South America the Guadua blossoms so very seldom that in the course of

four years we were only twice able to procure the flowers; once on the

solitary banks of the Cassiquiare, the arm connecting the Orinoco with

the Rio Negro and the Amazon, and again in the province of Popayan,

between Buga and Quilichao. It is a very striking fact that some

plants grow with the greatest vigour in certain localities without

flowering; as is the case with the European olive-trees introduced

into America centuries ago, and growing between the tropics, near

Quito, at elevations of about 9600 feet above the level of the sea;

and in like manner the walnuts, hazel-nut bushes, and the fine

olive-trees (_Olea Europea_) of the Isle of France.[QH]

As some of the Bambusaceæ (arborescent grasses) advance into the

temperate zone, so also they do not suffer in the torrid zone from the

temperate climate of mountain districts. They are certainly more

luxuriant as social plants between the sea-shore and elevations of

about 2558 feet in the Province de las Esmeraldas, west of the volcano

of Pichincha, where Guadua angustifolia (Bambusa Guadua of our

_Plantes équinoxiales_, t, i. tab. xx) generates in its interior large

quantities of the siliceous Tabaschir (Sanscrit _tvakkschira_,

cow-milk). We saw the Guadua advance in the pass of Quindiu, in the

chain of the Andes, to a height of 5755 feet above the level of the

sea, as determined by barometric measurements. Nastus borbonicus has

been called a true Alpine plant by Bory de St. Vincent, and according

to him it does not descend lower than 3840 feet on the declivity of

the volcano in the island of Bourbon. This appearance or the

repetition at great elevations of certain forms belonging to torrid

plains calls to mind the group of Alpine palms (Kunthia montana,

Ceroxylon andicola, and Oreodoxa frigida) of which I have already

spoken, and a grove of Musaceæ (Heliconia, perhaps Maranta), 16 feet

high, which I found growing isolated on the Silla de Caracas, at a

height of more than 7000 feet above the level of the sea.[QI] While

the form of gramineæ, with the exception of some few herbaceous

dicotyledons, constitutes the highest phanerogamic zone on the

snow-crowned summits of mountains, so the grasses mark the boundary of

phanerogamic vegetation in a horizontal direction, towards the

northern and southern polar regions.

Many admirable general results, no less than a great mass of important

materials, have been yielded to the geography of plants by my young

friend, Joseph Hooker, who, after having but recently returned with

Sir James Boss from the frozen antarctic regions, is now engaged in

exploring the Thibetian Himalaya. He draws attention to the fact that

phanerogamic flowering plants (grasses) advance 17½° nearer to the

north than to the south pole. In the Falkland Islands, near the thick

knots of Tussac grass, Dactylis cæspitosa, Forster. (a Festuca,

according to Kunth), and in Tierra del Fuego, under the shade of the

birch-leaved Fagus antarctica, there grows the same Trisetum

subspicatum, which spreads over the whole range of the Peruvian Andes,

and across the Rocky Mountains, to Melville Island, Greenland, and

Iceland, and is also found in the Swiss and Tyrolese Alps as well as

in the Altai, in Kamtschatka, and in Campbell’s Island, south of New

Zealand, extending therefore over 127 degrees of latitude, or from 54°

south to 72° 50′ north lat. “Few grasses,” says Joseph Hooker,[QJ]

“have so wide a range as Trisetum subspicatum (Beauv.), nor am I

acquainted with any other arctic species which is equally an

inhabitant of the opposite polar regions.” The South Shetland Islands,

which are separated by Bransfield Straits from d’Urville’s “Terre de

Louis-Philippe” and from Peak Haddington, a volcano, 7046 feet high,

and situated in 64° 12′ south lat., have recently been visited by Dr.

Eights, a botanist from the United States. He found there (probably in

62° or 62¼° south lat.) a small grass, Aira antarctica,[QK] which is

“the most antarctic flowering plant hitherto discovered.”

Even in Deception Island, belonging to the same group, 62° 50′, only

lichens are met with, and no longer any species of grass; and in like

manner further south-east, in Cockburn’s Island (64° 12′) near

Palmer’s Land, only Lecanoras, Lecideas, and five foliaceous Mosses,

among which is our German Bryum argenteum, were gathered. “This

appears to be the Ultima Thule of antarctic vegetation,” for further

south even terrestrial cryptogamia are wanting. In the great bay

formed by Victoria Land, on a small island lying opposite to Mount

Herschel (in 71° 49′ lat.), and on Franklin Island, 92 miles north of

the volcano, Erebus, (12,366 feet in height), and in 76° 7′ south

lat., Hooker found no trace of vegetation. In extreme northern

latitudes, the distribution of even the higher organisms is very

different; for here phanerogamic plants advance 18½° nearer to the

pole than in the southern hemisphere. Walden Island (80½° north lat.)

possesses still ten species of phanerogamia. Antarctic phanerogamic

vegetation is also poorer in species at equal distances from the pole;

thus Iceland has five times more phanerogamia than the southern group

of Auckland and Campbell Islands, but the uniform vegetation of the

antarctic regions is, from climatic causes, both more succulent and

more luxuriant.[QL]

Footnote 98:

p. 229—“_Ferns_.”

If we estimate the whole number of the cryptogamia hitherto described

at 19,000 species, as has been done by Dr. Klotzsch, a naturalist

possessing a profound acquaintance with the Agamic plants, we shall

have for Fungi 8000 (of which Agarici constitute the eighth part); for

Lichens, according to J. von Flotow of Hirschberg, and Hampe of

Blankenburg, at least 1400; for the Algæ 2580; for Mosses and

Liverworts, according to Carl Müller of Halle, and Dr. Gottsche of

Hamburgh, 3800; and for Ferns 3250. For this last important result we

are indebted to the profound investigations made by Professor Kunze of

Leipzig, on this group of plants. It is a striking fact that the

family of the Polypodiaceæ alone includes 2165 of the whole number of

described Filices, whilst other forms, as the Lycopodiacæ and

Hymenophyllaceæ, number only 350 and 200. There are therefore nearly

as many described species among Ferns as among Grasses.

It is singular that no mention of the beautiful arborescent ferns is

to be found in the classic authors of antiquity, Theophrastus,

Dioscorides, and Pliny; while, from the information given by the

companions of Alexander, Aristobulus, Megasthenes, and Nearchus,

reference is made[QM] to Bamboos, “quæ fissis internodiis lembi vice

vectitabant navigates;” to the Indian trees “quarum folia non minora

clypeo sunt;” to the Fig-tree which takes root from its branches, and

to Palms, “tantæ proceritatis, ut sagittis superjici nequeant.” I find

the first mention of arborescent ferns in Oviedo.[QN] “Among ferns,”

says this experienced traveller, who had been appointed by Ferdinand

the Catholic, Director of the Goldwashings in Haiti, “there are some

which I class with trees, because they are as thick and high as

Pine-trees. (Helechos que yo cuento por arboles, tan gruesos como

grandes pinos y muy altos). They mostly grow among the mountains and

where there is much water.” This estimate of their height is

exaggerated, for in the dense forests near Caripe even our Cyathea

speciosa only attains a height of 32 to 37 feet; and an admirable

observer, Ernst Dieffenbach, did not see in the most northern of the

three islands of New Zealand any trunks of Cyathea dealbata exceeding

42½ feet. In the Cyathea speciosa and the Meniscium of the Chaymas

missions, we observed in the midst of the most shady part of the

primeval forest, that the scaly stems of some of the most luxuriantly

developed of these trees were covered with a shining carbonaceous

powder, which appeared to be owing to a singular decomposition of the

fibrous parts of the old leaf stalks.[QO]

Between the tropics, where, on the declivities of the Cordilleras,

climates are superimposed in strata, the true region of arborescent

ferns lies between about 3200 and 5350 feet above the level of the

sea. In South America and in the Mexican highlands they seldom descend

lower towards the plains than 1280 feet. The mean temperature of this

happy region is between 64°.6 and 70°.8 Fahr. It reaches the lowest

stratum of clouds (which floats the nearest to the surface of the sea

and the plain), and it therefore enjoys uninterruptedly a high degree

of humidity, together with a great equality in its thermal

relations.[QP] The inhabitants, who are of Spanish descent, call this

region “Tierra templada de los helechos.”

The Arabic designation for ferns is _feledschun_, filix, (from which

the _f_ has been changed, according to Spanish usage, into _h_,) and

perhaps the term may be connected with the verb _faladscha_, “it

divides,” from the finely cut margin of the frond.[QQ]

The conditions of genial mildness in an atmosphere charged with

aqueous vapour and of great uniformity in respect to moisture and

warmth, are fulfilled on the declivities of the mountains in the

valleys of the Andes, and more especially in the southern milder and

more humid hemisphere, where arborescent ferns advance not only to New

Zealand and Van Diemen’s Land (Tasmania), but even as far as the

Straits of Magellan and Campbell Island, and therefore to a southern

latitude almost identical in degrees with the parallel in which Berlin

is situated north of the equator. From among the family of arborescent

ferns there flourishes the vigorous Dicksonia squarrosa, in 46° south

lat. in Dusky Bay, New Zealand; D. antarctica of Labillardière in

Tasmania; a Thyrsopteris in the Island of Juan Fernandez; an

undescribed Dicksonia, whose stem is from 12 to 16 feet high, near

Valdivia in Southern Chili; and a Lomaria, somewhat less in height, in

the Straits of Magellan. Campbell Island is still nearer to the south

pole, in 52½° lat., but even there the leafless stem of the Aspidium

venustum rises to a height of more than four feet.

The climatic relations under which Ferns (_Filices_) in general

flourish, are manifested in the numerical laws of their quotients of

distribution. In the plains within the tropical regions of large

continents this quotient is, according to Robert Brown, and from more

recent investigations on the subject, ¹⁄₂₀ of all the phanerogamia,

and in mountainous districts of large continents ⅙ to ⅛. This ratio is

quite different on the small islands scattered over the ocean; for

here the proportion borne by the number of ferns to the sum total of

all the phanerogamic plants increases so considerably, that in the

South-Sea Islands the quotient rises to ¼, while in the sporadic

islands, St. Helena and Ascension, the number of ferns is almost equal

to half of the whole phanerogamic vegetation.[QR] In receding from the

tropics (where on the large continents d’Urville estimates the

proportional number at ¹⁄₂₀), the _relative_ frequency of ferns

decreases rapidly as we advance into the temperate zone. The quotients

are for North America and the British Islands ¹⁄₃₅, for France ¹⁄₅₈,

for Germany ¹⁄₅₂, for the dry parts of Southern Italy ¹⁄₇₄, for Greece

¹⁄₈₄. The _relative_ frequency again increases considerably towards

the frigid north. Here the family of ferns decreases much slower in

the number of its species than does that of phanerogamic plants. The

luxuriantly aspiring character of the species, and the number of

individuals contained in each, augment the deceptive impression of

_absolute_ frequency. According to Wahlemberg’s and Hornemann’s

catalogues, the relative numbers of the Filices are for Lapland ¹⁄₂₅,

for Iceland ¹⁄₁₈, for Greenland ¹⁄₁₂.

Such are, according to our present knowledge, the natural laws that

manifest themselves in the distribution of the graceful form of Ferns.

But it would seem as if in the family of Ferns, which have so long

been regarded as cryptogamic, we had lately acquired evidence of the

existence of another natural law,—the morphological law of

propagation. Count Leszczyc-Suminski, who happily combines the power

of microscopic investigation with a very remarkable artistic talent,

has discovered an organisation capable of effecting fructification in

the prothallium of ferns. He distinguishes two sexual apparatuses, of

which the female portion is situated in hollow ovate cells in the

middle of the sporangium, and the male in the ciliated antheridia, or

the organs producing spiral threads, which have already been examined

by Nägeli. Fructification is supposed to be effected by means of

moveable ciliated spiral threads and not by pollen tubes.[QS]

According to this view, Ferns would be, as Ehrenberg remarks,[QT]

products of a microscopic fructification taking place on the

prothallium, which here serves as a fertilizing receptacle, while

throughout the whole course of their often arborescent development

they would be flowerless and fruitless plants, having a bud-formation.

The spores lying as sori on the under side of the frond are not seeds

but flower-buds.

Footnote 99:

p. 229—“_The Liliaceæ_.”

Africa is the principal seat of this form; there the greatest

diversity obtains; there they form masses and determine the natural

character of the region. The New Continent exhibits also, it is true,

magnificent Alströmeriæ and species of Pancratium, Hæmanthus, and

Crinum. We have enriched the first of these genera with nine, and the

second with three species; but these American liliaceous plants are

more diffused and of less social habits than the European Irideæ.

Footnote 100:

p. 229—“_The Willow Form_.”

Nearly 150 different species of the main representatives of this form,

or rather of the Willow itself, are already known. They cover the

northern parts of the earth from the equator to Lapland. Their number

and their varieties of form increase between the 46th and 70th degrees

of latitude, more especially in that part of northern Europe which has

been so remarkably indented by the early revolutions of our planet. I

am acquainted with ten or twelve species of inter-tropical Willows,

and these, like the Willows of the southern hemisphere, are deserving

of special attention. As nature appears to delight in all zones in a

wondrous multiplication of certain animal forms, as for instance,

Anatidæ (_Lamellirostres_), and Pigeons; so likewise are Willows,

Pines, and Oaks, widely diffused; the latter always exhibiting a

similarity in their fruit, although various differences exist in the

form of the leaves. In Willows belonging to the most widely different

climates the similarity of the foliage, of the ramification, and of

the whole physiognomical conformation, is almost greater than in

Coniferæ. In the more southern part of the temperate zone, north of

the equator, the number of the species of Willows decreases

considerably; although (according to the “Flora atlantica” of

Desfontaines) Tunis has still its own species, resembling Salix

caprea; whilst Egypt, according to Forskäl, numbers five species, from

the catkins of whose male blossoms is distilled the remedial agent

Moie chalaf (_aqua salicis_), so much used in the East. The Willow

which I saw in the Canaries is also, according to Leopold von Buch and

Christian Smith, a peculiar species (_S. canariensis_), although

common to those islands and to Madeira. Wallich’s catalogue of the

plants of Nepaul and the Himalaya already gives 13 species belonging

to the subtropical zone of the East Indies, and which have in part

been described by Don, Roxburgh, and Lindley. Japan has its own

species, of which one, S. japonica. (Thunb.), is also met with in

Nepaul as an Alpine plant.

There was not, as far as I am aware, any species of Willow known as

belonging to the tropical zone before my expedition, with the

exception of S. tetrasperma. We collected seven new species, three of

them on the plateaux of Mexico, at an elevation of 8500 feet above the

level of the sea. Still higher, as for instance on the Alpine plains,

between 12,000 and 15,000 feet, which we frequently visited, we saw

nothing in the Andes of Mexico, Quito, and Peru, to remind us of the

many small creeping Alpine Willows of the Pyrenees, the Alps, or of

Lapland (_S. herbacea_, _S. lanata_, and _S. reticulata_). In

Spitzbergen, whose meteorological relations have so much analogy with

those of the snow-crowned summits of Switzerland and Scandinavia,

Martius described two Dwarf-Willows, whose small woody stems and

branches trail along the ground, and are so concealed in the turf-bogs

that it is with difficulty their diminutive leaves can be discovered

under the moss. The Willow species which I found in 4° 12′ south lat.,

at the entrance of the Cinchona or Peruvian Bark forests, near Loxa in

Peru, and which has been described by Willdenow as Salix Humboldtiana,

is most widely diffused over the western part of South America. A

Beach-Willow (_S. falcata_), which we discovered on the sandy shores

of the Pacific, near Truxillo, is, according to Kunth, probably a mere

variety of the former. In like manner the beautiful and frequently

pyramidal Willow, which we constantly saw on the banks of the

Magdalena river, from Mahates to Bojorque, and which, according to the

report of the natives, had only spread thus far within a few years,

may also be identical with S. Humboldtiana. At the confluence of the

Magdalena with the Rio Opon, we found all the islands covered with

Willows, many of which had stems 64 feet high, with a diameter of from

only 8 to 10 inches.[QU] Lindley has made us acquainted with a species

of Salix belonging to Senegal, and therefore to the equinoctial region

of Africa.[QV] Blume also found two species of Willow near the equator

in Java, one wild and indigenous in the island (_S. tetrasperma_), and

another cultivated (_S. Sieboldiana_). I am only acquainted with the

two Willows belonging to the south temperate zone, which have been

described by Thunberg (_S. hirsuta_ and _S. mucronata_). They grow

interspersed with Protea argentea, which has the same physiognomy as

the Willow, and their leaves and young branches constitute the food of

the hippopotamus of the Orange River. The family of Willows is

entirely wanting in Australia and the neighbouring islands.

Footnote 101:

p. 229—“_The Myrtle Form_.”

The Myrtle is a graceful plant, with stiff, shining, crowded, and

generally entire and small leaves marked with dots. Myrtles impart a

peculiar character to three regions of the earth, viz., to southern

Europe, more especially to the islands composed of calcareous rocks

and trachytic stone, which project from the basin of the

Mediterranean; to the continent of New Holland, which is adorned with

Eucalyptus, Metrosideros, and Leptospermum; and to an inter-tropical

region in the Andes of South America, part of which is a low plain,

while the remainder lies at an elevation of from 9000 to more than

10,000 feet above the level of the sea. This Alpine region, called in

Quito the Paramos, is entirely covered with trees having a Myrtle-like

aspect, even though they may not all belong to the Myrtaceæ. At this

elevation grow Escalonia myrtilloides, E. tubar, Simplocos Alstonia,

species of Myrica, and the lovely Myrtus microphylla, of which we have

given a drawing in our _Plantes équinoxiales_, t. i. p. 21, pl. iv.;

it grows on micaceous schist, at an elevation of 10,000 feet on the

Paramo de Saraguru, (near Vinayacu and Alto de Pulla,) which is

adorned with so many beautiful flowering Alpine plants. M. myrsinoides

ascends in the Paramo de Guamani as high as 11,200 feet. By far the

greater number of the 40 species of the genus Myrtus which we

collected in the equinoctial zone, and of which 37 were undescribed,

belong to the plains and the less elevated mountain spurs. We brought

only a single species (_M. xalapensis_) from the mild tropical climate

of the mountains of Mexico; but the Tierra templada, in the direction

of the Volcano of Orizaba, no doubt possesses many yet undescribed

varieties. We found M. maritima near Acapulco, on the very shore of

the Pacific.

The _Escalloniæ_,—among which _E. myrtilloides_, _E. tubar_, _E.

floribunda_ are the ornaments of the Paramos, and remind us strongly

(by their physiognomical aspect) of the myrtle-form,—formerly

constituted, together with the European and South American Alpine

roses (Rhododendrum and Befaria), with Clethra, Andromeda, and

Gaylussacia buxifolia, the family of the _Ericeæ_. Robert Brown[QW]

has arranged them in a special family, which Kunth has placed between

the Philadelphiæ and Hamamelideæ. Escallonia floribunda affords by its

geographical distribution one of the most striking examples of the

relation existing between distance from the equator and vertical

elevation above the level of the sea. I would here again borrow

support from the testimony of the accurate observer, my friend Auguste

de St. Hilaire.[QX] “MM. Humboldt and Bonpland in their expedition

discovered Escallonia floribunda in 4° south lat. at an elevation of

8952 feet. I found the same plant in 21° south lat. in Brazil, which

although elevated is very much less so than the Andes of Peru. This

plant is of common occurrence between 24° 50′ and 25° 55′ in the

Campos Geraes, and I also met with it again on the Rio de la Plata in

about 35° lat., on a level with the sea.”

The group of the Myrtaceæ,—to which belong Melaleuca, Metrosideros,

and Eucalyptus, commonly classed under the general denomination of

Leptospermeæ,—produce partially, wherever the true leaves are supplied

by phyllodia (petiole-leaves), or where the direction of the leaves is

inclined towards the unexpanded petiole, a distribution of streaks of

light and shade wholly unknown in our deciduous-leaved forest. We find

that the earliest botanical travellers who visited New Holland were

astonished at the singular effect thus produced. Robert Brown was the

first to show that this phenomenon depends on the vertical direction

of the expanded petioles (the phyllodia of Acacia longifolia and

Acacia suaveolens), and on the circumstance, that the light, instead

of falling on horizontal surfaces, passes between vertical ones.[QY]

Morphological laws in the development of the leaves determine the

peculiar character of the varying light and shade. “Phyllodia,” says

Kunth, “can in my opinion merely occur in families which have compound

pinnate leaves; and in fact they have as yet only been met with in

Leguminosæ (in the Acacias). In Eucalyptus, Metrosideros, and

Melaleuca, the leaves are simple (simplicia), and their edgewise

position depends on a half-turn of the leaf-stalk (petiolus);

moreover, it must be remarked, that both surfaces of the leaves are of

a similar character.” In the scantily shaded forests of New Holland

the optical effects here alluded to are the more frequent, since two

groups of Myrtaceæ and Leguminosæ, species of Eucalyptus and Acacia,

there constitute nearly one-half of all the greyish-green tree

vegetation. Moreover, between the bast-layers of Melaleuca, there are

formed easily soluble membranes, which force their way outwards, and

by their whiteness reminds us of our birch bark.

The sphere of distribution of the Myrtaceæ is very different in the

two continents. In the New Continent, and especially in its western

parts, this family, according to Joseph Hooker,[QZ] scarcely extends

beyond the parallel of 26° north lat., while in the Southern

Hemisphere, there are in Chili, according to Claude Gay, ten species

of Myrtle and twenty-two of Eugenia, which mixed with Proteaceæ

(Embothrium and Lomatia) and with Fagus obliqua, there constitute

forests. The Myrtaceæ become more frequent from the 38th degree of

south lat.; in the island of Chiloe, where a metrosideros-like species

(Myrtus stipularis) forms almost impenetrable underwood, which is

there named Tepuales; and in Patagonia to the extremity of Tierra del

Fuego in 56° lat. While in Europe the Myrtaceæ do not extend northward

further than 46° lat., they penetrate in Australia, Tasmania, New

Zealand and the Auckland Islands to 50½° south latitude.

Footnote 102:

p. 229—“_Melastomaceæ_.”

This group comprises the genera Melastoma (Fothergilla and Tococa Aub.

and Rhexia (Meriana and Osbeckia), of which we have collected no less

than sixty new species in tropical America alone, on both sides of the

equator. Bonpland has published a splendid work on the Melastomaceæ,

in two volumes, with coloured plates. There are species of Rhexia and

Melastoma which ascend in the chain of the Andes, as Alpine or Paramos

shrubs, to 9600 and even more than 11,000 feet above the level of the

sea; as for instance Rhexia cernua, R. stricta, Melastoma obscurum, M.

aspergillare, and M. lutescens.

Footnote 103:

p. 229—“_The Laurel-form_.”

To this form belong Laurus, Persea, the Ocoteæ, so numerous

in South America, and,—on account of their physiognomic

similarity,—Calophyllum, also the splendidly aspiring Mammea from the

Guttiferæ.

Footnote 104:

p. 229—“_How instructive to the landscape-painter would be a work

which should illustrate the leading forms of vegetation_.”

In order to define with more distinctness what I have here only

briefly referred to, I may be permitted to incorporate the following

considerations from my sketch of a history of landscape painting, and

of a graphical representation of the physiognomy of plants.[RA]

“All that relates to the expression of the passions and the beauty of

the human form has perhaps attained its fullest development in the

temperate northern zone under the skies of Greece and Italy. The

artist, drawing from the depths of imagination, no less than from the

contemplation of beings of his own species, derives the types of

historical painting alike from unfettered creation and from truthful

imitation. Landscape painting, though scarcely a more imitative art,

has a more material basis, and a more earthly tendency. It requires

for its development a greater amount of various and distinct

impressions, which, when imbibed from external contemplation, must be

fertilized by the powers of the mind in order to be presented to the

senses of others as a creative work of art. The grander style of

heroic landscape-painting is the combined result of a profound

appreciation of nature, and of this inward process of the mind.

“Everywhere, in every separate portion of the earth, nature is indeed

only a reflex of the whole. The forms of organization recur again and

again in different combinations. Even the icy north is cheered for

months together by the presence of herbs and large Alpine blossoms

covering the earth, and by a mild azure sky. Hitherto landscape

painting among us has pursued her graceful labours familiar only with

the simpler forms of our native floras, but not therefore without

depth of feeling and richness of creative fancy. Dwelling only on the

native and indigenous form of our vegetation, this branch of art,

notwithstanding that it has been circumscribed by such narrow limits,

has yet afforded sufficient scope for highly-gifted painters, such as

the Caracci, Gaspar Poussin, Claude Lorraine, and Ruysdael, to produce

the happiest and most varied creations of art, by their magical power

of managing the grouping of trees, and the effects of light and shade.

That progress which may still be expected in art, from a more animated

intercourse with the tropical world, and from ideas engendered in the

mind of the artist by the contemplation of Nature in her grandest

forms, will never diminish the fame of the old masters. I have alluded

to this, to recal the ancient bond which unites a knowledge of Nature

with poetry and a taste for art. For in landscape painting, as in

every other branch of art, a distinction must be drawn between the

elements generated by a limited field of contemplation and direct

observation, and those which spring from the boundless depth of

feeling, and from the force of idealising mental power. The grand

conceptions which landscape painting, as a more or less inspired

branch of the poetry of nature, owes to the creative power of the

mind, are, like man himself, and the imaginative faculties with which

he is endowed, independent of place. These remarks especially refer to

the gradations in the form of trees from Ruysdael and Everdingen,

through the works of Claude Lorraine, to Poussin and Annibal Caracci.

In the great masters of art there is no indication of local

limitation. But an extension of the visible horizon, and an

acquaintance with the nobler and grander forms of nature, and with the

luxuriant fulness of life in tropical regions, afford the advantage of

not simply enriching the material groundwork of landscape-painting,

but also of inducing more vivid impressions in the minds of less

highly gifted painters, and thus heightening their powers of artistic

creation.”

Footnote 105:

p. 230—“_From the thick and rough bark of the Crescentiæ and

Gustaviæ_.”

In _Crescentia Cujete_ (the Tutuma tree, whose large fruit-shells are

so indispensable to the natives as household utensils), in

_Cynometra_, the Cacao-tree (_Theobroma_), and the _Perigara Gustavia_

(Linn.), the tender blossoms burst forth from the half-carbonized

bark. When children eat the fruit of the _Pirigara speciosa_ (the

_Chupo_), their whole bodies become tinged with yellow; and this

jaundice, after a continuance of from twenty-four to thirty-six hours,

disappears without the use of medicine.

An indelible impression was produced on my mind by the luxuriant power

of vegetation in the tropical world, when, on entering a Cacao

plantation (_Caca hual_), in the Valles de Aragua, after a damp night,

I saw for the first time large blossoms springing from the root of a

_Theobroma_, deeply imbedded in the black soil. This is one of the

most instantaneous manifestations of the activity of the vegetative

force of organisation. Northern nations speak of “the awakening of

Nature at the first genial breath of Spring;”—expressions that

strongly contrast with the imaginative complaint of the Stagirite, who

regarded vegetable forms as buried in a “still sleep, from which there

is no awakening, and free from the desires that excite to spontaneous

motion.”[RB]

Footnote 106:

p. 230—“_Draw on their heads as caps_.”

These are the flowers of our _Aristolochia cordata_, to which

reference has been made in Illustration 25. The largest flowers in the

world, besides those belonging to the Compositæ (the Mexican

_Helianthus annuus_), are produced by _Rafflesia Arnoldi_,

_Aristolochia_, _Datura_, _Barringtonia_, _Gustavia_, _Carolinea_,

_Lecythis_, _Nymphæa_, _Nelumbium_, _Victoria Regina_, _Magnolia_,

_Cactus_, the Orchideæ, and the Liliaceous forms.

Footnote 107:

p. 231—“_The luminous worlds which spangle the firmament from pole to

pole_.”

The more magnificent portion of the southern sky, in which shine the

constellations of the Centaur, Argo, and the Southern Cross, where the

Magellanic clouds shed their pale light, is for ever concealed from

the eyes of the inhabitants of Europe. It is only under the equator

that man enjoys the glorious spectacle of _all_ the stars of the

southern and northern heavens revealed at one glance. Some of our

northern constellations,—as, for instance, Ursus Major and Ursus

Minor,—owing to their low position when seen from the region of the

equator, appear to be of a remarkable, almost fearful magnitude. As

the inhabitant of the tropics beholds _all_ stars, so too, in regions

where plains, deep valleys, and lofty mountains are alternated, does

Nature surround him with representatives of every form of vegetation.

* * * * *

In the foregoing sketch of a “Physiognomy of Plants,” I have

endeavoured to keep in view three nearly allied subjects,—_the

absolute diversity of forms_; their _numerical_ relations, _i.e._

their local preponderance in the whole number of phanerogamic floras;

and their _geographical and climatic distribution_. If we would rise

to a general view regarding vital forms;—the physiognomy, the study of

the numerical relations (the arithmetic of botany), and the geography

of plants (the study of the local zones of distribution), cannot, as

it seems to me, be separated from one another. The study of the

physiognomy of plants must not be exclusively directed to the

consideration of the striking contrasts of form which the larger

organisms present, when considered separately; but it must rise to the

recognition of the laws which determine _physiognomy of nature

generally_, the picturesque character of vegetation over the whole

surface of the earth, and the vivid impression produced by the

grouping of contrasted forms in different zones of latitude and

elevation. It is when concentrated into this focus that we first

clearly perceive the close and intimate connection existing between

the subjects treated of in the preceding pages. We have here entered

upon a field of inquiry hitherto but little cultivated. I have

ventured to follow the method first propounded with such brilliant

results in Aristotle’s zoological works, and which is so especially

adapted to establish scientific confidence,—a method in which the

incessant effort to arrive at a generalisation of ideas supported by

individual illustrations, is associated with an endeavour to penetrate

to the specialities of phenomena.

The enumeration of forms is, from the physiognomical difference of

their nature, incapable of any strict classification. Here, as

everywhere in the consideration of external forms, there are certain

main types which present the strongest contrasts,—as the groups of the

Arborescent Grasses, the Aloe form and the species of Cactus, Palms,

Acicular-leaved trees, Mimosaceæ, and Bananas. Even scantily dispersed

individuals belonging to these groups determine the character of a

district, and produce a lasting impression on the mind of the

unscientific but susceptible beholder. Other forms, perhaps more

numerous and preponderating, may not appear equally marked either by

the shape or position of the leaves; the relation of the stem to the

branches, luxuriant vigour, animation, and grace; or even by the

melancholy contraction of the leaf-organs.

As, therefore, a physiognomical classification, or a distribution into

groups according to external appearance, does not admit of being

applied to the whole vegetable kingdom collectively, the basis on

which such a classification should be grounded must necessarily be

wholly different from that which has been so happily chosen for the

establishment of our comprehensive systems of the natural families of

plants. Vegetable physiognomy grounds its divisions and the choice of

its types on all that possesses mass,—as the stem, branches, and

appendicular organs (the form, position, and size of the leaf, the

character and brilliancy of the parenchyma), and consequently on all

that is now included under the special term, _the organs of

vegetation_, and on which depend the preservation (nourishment and

development) of the individual; while systematic botany, on the other

hand, bases the arrangement of the natural families of plants on a

consideration of the organs of propagation, on which depends the

preservation of the species.[RC] It was already taught in the school

of Aristotle,[RD] that the generation of seed is the ultimate aim of

the being and life of a plant. The process of development in the

organs of fructification has become, since Caspar Fried. Wolf,[RE] and

our great poet Goëthe, the morphological basis of all systematic

botany.

This science and that also of vegetable physiognomy proceed, I would

here again observe, from two different points of view; the former

depending upon an accordance in the inflorescence and in the

reproduction of the delicate sexual organs; the latter on the

conformation of the parts constituting the axes (the stem and

branches) and on the outline of the leaves, which are mainly

determined by the distribution of the vascular bundles. As, moreover,

the stem and branches, together with their appendicular organs,

predominate by mass and volume, they determine and strengthen the

impression we receive, while they individualize the physiognomical

character of the vegetation, as well as that of the landscape or the

zone in which some distinguished types occur. The law is here

expressed by the accordance and affinity in the marks appertaining to

the vegetative, _i.e._ the nutritient organs. In all European colonies

the inhabitants have been led by resemblances of physiognomy

(_habitus_, _facies_) to apply the names of European forms to certain

tropical plants, which bear wholly different flowers and fruits from

the genera to which these designations originally referred. Everywhere

in both hemispheres, the northern settler has believed he could

recognise Alders, Poplars, Apple and Olive trees; being misled for the

most part by the form of the leaves and the direction of the branches.

The charm associated with the remembrance of native forms has

strengthened the illusion, and European names of plants have thus been

perpetuated from generation to generation in the slave colonies, where

they have been further enriched by denominations borrowed from the

negro languages.

A remarkable phenomenon is presented by the contrast frequently

observed to arise from a striking accordance in physiognomy, coupled

with the greatest difference in the organs of inflorescence and

fructification—between the external form as determined by the

appendicular or leaf-system, and the sexual organs on which are based

the various groups of the natural systems of botany. One would be

disposed _à priori_ to believe that the aspect of vegetative organs

(leaves) exclusively so called, must depend upon the structure of the

organs of reproduction, but this dependence has only been observed in

a very small number of families, as Ferns, Grasses, Cyperaceæ, Palms,

Coniferæ, Umbelliferæ, and Aroideæ. In the Leguminosæ this accordance

between the physiognomical character and the inflorescence can

scarcely be recognized, excepting where they are separated into groups

(as Papilionaceæ, Cæsalpinineæ, and Mimosaceæ.) The types which

exhibit, when compared together, a very different structure of

inflorescence and fructification, notwithstanding external accordance

in physiognomy, are Palms and Cycadeæ, the latter being most nearly

allied to the Coniferæ; _Cucusta_, belonging to the Convolvulaceæ, and

the leafless _Cassytha_, a parasitical Laurinea; _Equisetum_ (from the

division of the Cryptogamia) and _Ephedra_ (a coniferous tree). The

Grossulareæ (_Ribes_) are so nearly allied by their efflorescence to

Cactuses, _i. e._ the family of the Opuntiaceæ, that it is only very

lately that they have been separated from them! One common family

(that of the Asphodeleæ) comprises the gigantic tree, _Dracœna Draco_,

the Common Asparagus, and the coloured flowering _Aletris_. Simple and

compound leaves frequently belong not only to the same family, but

even to the same genus. We found in the elevated plateaux of Peru and

New Granada among twelve new species of _Weinmannia_, five with

simple, and the remainder with pinnate leaves. The genus _Aralia_

exhibits yet greater independence in the leaf-form, which is either

simple, entire, lobed, digitate, or pinnate.[RF]

Pinnate leaves appear to me to belong especially to those families

which occupy the highest grade of organic development, as for

instance, the _Polypetalœ_; among _perigynic_ plants, the Leguminosæ,

Rosaceæ, Terebinthaceæ, and Juglandeæ; among _hypogynic_ plants the

Aurantiaceæ, Cedrelaceæ, and Sapindaceæ. The elegant form of the

doubly pinnate leaf, which constitutes so great an adornment of the

torrid zone, is most frequently met with among the Leguminosæ; among

the Mimosaceæ, and also among some Cæsalpinias, Coulterias and

Gleditschias; but never, as Kunth has observed, among the

Papilionaceæ.

The form of pinnate, and more especially of compound leaves, is

unknown in Gentianeæ, Rubiaceæ, and Myrtaceæ. In the morphological

development presented by the richness and varied aspect of the

appendicular organs of dicotyledons, we are only able to recognize a

very small number of general laws.

ON THE

STRUCTURE AND MODE OF ACTION

OF

VOLCANOS

IN DIFFERENT PARTS OF THE EARTH.

(This Memoir was read at a Public Meeting of the Academy, at Berlin, on

the 24th January, 1823.)

When we consider the influence exerted on the study of nature during the

last few centuries, by the extension of geographical knowledge and by

means of scientific expeditions to remote regions of the earth, we are

at once made sensible of the various character of this influence,

according as the investigations have been directed to the forms of the

organic world, the study of the inorganic crust of the earth, or to the

knowledge of rocks, their relative ages, and their origin. Different

vegetable and animal developments exist in every division of the earth,

whether it be on the plains, where, on a level with the sea, the

temperature varies with the latitude and with the various inflections of

the isothermal lines, or on the steep declivity of mountain ranges,

warmed by the direct rays of the sun. Organic nature imparts to every

region of the globe its own characteristic physiognomy. But this does

not apply to the inorganic crust of the earth divested of its vegetable

covering, for everywhere, in both hemispheres, from the equator to the

poles, the same rocks are found grouped with some relation to each

other, either of attraction or repulsion. In distant lands, surrounded

by strange forms of vegetation, and beneath a sky beaming with other

stars than those to which his eye had been accustomed, the mariner often

recognises, with joyful surprise, argillaceous schists and rocks

familiar to him in his native land.

This independence of geological relations on the actual condition of

climates does not diminish the beneficial influence exercised on the

progress of mineralogy and physical geognosy by the numerous

observations instituted in distant regions of the earth, but simply

gives a particular direction to them. Every expedition enriches natural

history with new genera of plants and animals. At one time we acquire a

knowledge of new organic forms which are allied to types long familiar

to us, and which not unfrequently, by furnishing links till then

deficient, enable us to establish, in all its original perfection, an

uninterrupted chain of natural structures. At another time we become

acquainted with isolated structures, which appear either as the remains

of extinct genera, or members of unknown groups, the discovery of which

stimulates further research. It is not, however, from the investigation

of the earth’s crust that we acquire these manifold additions to our

knowledge, for here we meet rather with an uniformity in the constituent

parts, in the superposition of dissimilar masses, and in their regular

recurrence, which cannot fail to excite the surprise and admiration of

the geologist. In the chain of the Andes, as in the mountains of Central

Europe, one formation appears, as it were, to call forth another. Masses

identical in character assume the same forms; basalt and dolerite

compose twin mountains; dolomite, sandstone, and porphyry form abrupt

rocky walls; while vitreous trachyte, containing a large proportion of

feldspar, rises in bell-shaped and high-vaulted domes. In the most

remote regions large crystals are separated in a similar manner from the

compact texture of the fundamental mass, and, blending and grouping

together into subordinate strata, frequently announce the commencement

of new and independent formations. It is thus that the inorganic world

may be said to reflect itself, more or less distinctly, in every

mountain of any great extent. It is necessary, however, in order

perfectly to understand the most important phenomena of the composition,

relative age, and origin of formations, to compare together the

observations made in regions of the earth most widely remote from each

other. Problems which have long baffled the geologist in his own

northern region, find their solution in the vicinity of the equator. If,

as we have already observed, remote regions do not present us with new

formations, that is to say, with unknown groupings of simple substances,

they at least help us to unravel the great and universal laws of nature,

by showing how different strata of the crust of the earth are mutually

superimposed on, and intersect, each other in the form of veins, or rise

to different elevations in obedience to elastic forces.

Although our geological knowledge may be thus extensively augmented by

researches over vast regions, it can hardly be a matter of surprise that

the class of phenomena constituting the principal subject of this

address should have been so long examined in an imperfect manner, since

the means of comparison were of difficult, and almost, it may be said,

of laborious access.

Until towards the close of the eighteenth century all that was known of

the form of volcanos and of the action of their subterranean forces was

derived from observations made on two volcanic mountains of Southern

Italy, Vesuvius and Etna. As the former of these was the more

accessible, and (like all volcanos of slight elevation) had frequent

eruptions, a hill became to a certain degree the type according to which

a whole world—the mighty volcanos of Mexico, South America, and the

Asiatic Islands—was supposed to be formed. Such a mode of reasoning

involuntarily calls to mind Virgil’s shepherd, who believed that in his

own humble cot he saw the image of the eternal city, Imperial Rome.

This imperfect mode of studying nature might indeed have been obviated

by a more attentive examination of the whole Mediterranean, and

especially of its eastern islands and littoral districts, where mankind

first awoke to intellectual culture and to a higher standard of feeling.

Among the Sporades, trachytic rocks have risen from the bottom of the

sea, and have formed lands similar to those of the Azores, which in the

course of three centuries have appeared periodically at three almost

equal intervals of time. Between Epidaurus and Trœzene, near Methone, in

the Peloponnesus, there is a Monte Nuovo, described by Strabo and since

by Dodwell. Its elevation is greater than that of the Monte Nuovo of the

Phlegræan fields near Baiæ, and perhaps even than that of the new

volcano of Xorullo, in the plains of Mexico, which I found to be

surrounded by many thousand small basaltic cones, upheaved from the

earth, and still emitting smoke. It is not only in the basin of the

Mediterranean, that volcanic fires escape from the permanent craters of

isolated mountains having a constant communication with the interior of

the earth, as Stromboli, Vesuvius, and Etna; for at Ischia, and on Mount

Epomeus, and also, according to the accounts of the ancients, in the

Lelantine plain, near Chalcis, lavas have flowed from fissures which

have suddenly opened on the surface of the earth. Besides these

phenomena, which fall within historical periods, that is, within the

narrow bounds of authentic tradition, and which Ritter purposes

collecting and explaining in his masterly work on geography, the shores

of the Mediterranean present numerous remains of the earlier action of

fire. The south of France exhibits in Auvergne a distinct and peculiar

system of volcanos, linearly arranged, trachytic domes alternating with

cones of eruption, emitting lava streams in the form of bands. The

plains of Lombardy, which are on a level with the sea, and constitute

the innermost bay of the Adriatic, inclose the trachyte of the Euganean

Hills, where rise domes of granular trachyte, obsidian, and pearl-stone.

These masses are developed from each other, and break through the lower

chalk formations and nummulitic limestone, but have never been emitted

in narrow streams. Similar evidence of former revolutions of our earth,

is afforded in many parts of the Greek Continent and in Western Asia,

countries which will undoubtedly some day yield the geologist ample

materials for investigation, when the light of knowledge shall again

shine on those lands whence it first dawned on our western world, and

when oppressed humanity shall cease to groan beneath the weight of

Turkish barbarism.

I allude to the geographical proximity of such numerous and various

phenomena in order to show that the basin of the Mediterranean, with its

series of islands, might have enabled the attentive observer to note all

those phenomena which have recently been discovered under various forms

and structures in South America, Teneriffe, and in the Aleutian islands,

near the Polar region. The materials for observation were, no doubt,

accumulated within a narrow compass; but it was yet necessary that

travels in distant countries and comparisons between extensive tracts of

land, both in and out of Europe, should be undertaken, in order to

obtain a correct idea of the resemblance between volcanic phenomena and

of their dependence on each other.

Language, which so frequently imparts permanence and authority to first,

and often also erroneous views, but which points, as it were,

instinctively to the truth, has applied the term _volcanic_ to all

eruptions of subterranean fire and molten matter; to columns of smoke

and vapour which ascend sporadically from rocks, as at Colares, after

the great earthquake of Lisbon; to Salses, or argillaceous cones

emitting moist mud, asphalt, and hydrogen, as at Girgenti in Sicily, and

at Turbaco in South America; to hot Geyser springs, which rise under the

pressure of elastic vapours; and, in general, to all operations of

impetuous natural forces which have their seat deep in the interior of

our planet. In Central America (Guatimala) and in the Philippine

Islands, the natives even formally distinguish between _Volcanes de agua

y de fuego_, volcanos emitting water, and those emitting fire;

designating by the former appellation, mountains from which subterranean

waters burst forth from time to time, accompanied by a dull hollow sound

and violent earthquakes.

Without denying the connection, which undoubtedly exists among the

phenomena just referred to, it would seem advisable to apply more

definite terms to the physical as well as to the mineralogical portion

of the science of geology, and not at one time to designate by the word

_volcano_ a mountain terminating in a permanent fire-emitting mouth, and

at another to apply it to any subterranean cause, be it what it may, of

volcanic action. In the present condition of our earth, the form of

isolated conical mountains (as those of Vesuvius, Etna, the Peak of

Teneriffe, Tunguragua and Cotopaxi) is certainly the shape most commonly

observed in volcanos. I have myself seen such volcanos varying in height

from the most inconsiderable hill to an elevation of more than 19,000

feet above the level of the sea. Besides such conical forms, however, we

continually meet with permanent fire-emitting mouths, in which the

communication with the interior of the earth is maintained on

far-extended jagged ridges, and not even always from the centre of their

mural summits, but at their extremity towards their slope. Such, for

instance, is Pichincha, situated between the Pacific and the city of

Quito, which has acquired celebrity from Bouguer’s earliest barometric

formulæ, and such are the volcanos on the Steppe de los Pastos, situate

at more than 10,000 feet above the level of the sea. All these variously

shaped summits consist of trachyte, formerly known as trap-porphyry; a

granular stone full of narrow fissures, composed of different kinds of

feldspar (labradorite, oligoklase, and albite), augite, hornblende, and

sometimes interspersed mica, and even quartz. Wherever the evidences of

the first eruption, the ancient structures—if I may use the

expression—remain complete, the isolated cone is surrounded,

circus-like, with a high wall of rock consisting of different

superimposed strata, encompassing it like an outer sheath. Such walls or

circular inclosures are termed _craters of elevation_, and constitute a

great and important phenomenon, upon which that eminent geologist,

Leopold von Buch, from whose writings I have borrowed many facts

advanced in this treatise, presented so remarkable a paper to our

Academy five years ago.

Volcanos which communicate with the atmosphere by means of fire-emitting

mouths, such as conical basaltic hills, and dome-like craterless

trachytic mountains, (the latter being sometimes low, like the Sarcouy,

and sometimes high, like the Chimborazo,) form various groups.

Comparative geography draws our attention, at one time, to small

Archipelagos or independent mountain-systems, with craters and lava

streams, like those in the Canary Isles and the Azores, and without

craters or true lava streams, as in the Euganean hills, and the

Siebengebirge near Bonn; at another time, it makes us acquainted with

volcanos arranged in single or double chains, and extending for many

hundred miles in length, either running parallel with the main direction

of the range, as in Guatimala, Peru, and Java, or intersecting its axis

at right angles, as in tropical Mexico. In this land of the Aztecs

fire-emitting trachytic mountains alone attain the high snow limit: they

are ranged in the direction of a parallel of latitude, and have probably

been upheaved from a chasm extending over upwards of 420 miles,

intersecting the whole continent from the Pacific to the Atlantic.

This crowding together of volcanos, either in rounded groups or double

lines, affords the most convincing proof that their action does not

depend on slight causes located near the surface, but that they are

great and deep-seated phenomena. The whole of the eastern portion of the

American continent, which is poor in metals, has in its present

condition no fire-emitting openings, no trachytic masses, and perhaps no

basalt containing olivine. All the volcanos of America are united in the

portion of the continent opposite to Asia, along the chain of the Andes,

which runs nearly due north and south over a distance of more than 7200

miles.

The whole elevated table-land of Quito, which is surmounted by the high

mountains of Pichincha, Cotopaxi, and Tunguragua, constitutes one sole

volcanic hearth. The subterranean fire bursts sometimes from one and

sometimes from another of these openings, which have generally been

regarded as independent volcanos. The progressive movement of the fire

has, for three centuries, inclined from north to south. Even the

earthquakes, which so fearfully devastate this portion of the globe,

afford striking evidence of the existence of subterranean

communications, not only between countries where there are no

volcanos—as has long been known—but likewise between volcanic apertures

situated at a distance from each other. Thus the volcano of Pasto, east

of the river Guaytara, continued during three months of the year 1797,

to emit, uninterruptedly, a lofty column of smoke, until it suddenly

ceased at the moment of the great earthquake of Riobamba, (at a distance

of 240 miles,) and the mud eruption of the “Moya,” in which from thirty

to forty thousand Indians perished.

The sudden appearance, on the 30th of January, 1811, of the island of

Sabrina, in the group of the Azores, was the precursor of the dreadful

earthquakes which, further westward, shook, from May, 1811, to June,

1813, almost uninterruptedly, first the Antilles, then the plains of the

Ohio and Mississippi, and lastly, the opposite coasts of Venezuela or

Caracas. Thirty days after the total destruction of the beautiful

capital of the province, there was an eruption of the long inactive

volcano of St. Vincent, in the neighbouring islands of the Antilles. A

remarkable phenomenon accompanied this eruption: at the moment of this

explosion, which occurred on the 30th of April, 1811, a terrible

subterranean noise was heard in South America, over a district of more

than 35,000 square miles. The inhabitants of the banks of the Apure, at

the confluence of the Rio Nula, and those living on the remote sea-coast

of Venezuela, agreed in comparing this sound to the noise of heavy

artillery. The distance from the confluence of the Rio Nula with the

Apure (by which I entered the Orinoco) to the volcano of St. Vincent,

measured in a straight line, is no less than 628 miles. This noise was

certainly not propagated through the air, and must have arisen from some

deep-seated subterranean cause; its intensity was, moreover, hardly

greater on the shores of the Caribbean sea, near the seat of the raging

volcano, than in the interior of the country in the basin of the Apure

and the Orinoco.

It would be useless to multiply examples of this nature, by adducing

others which I have collected: I will therefore only refer to one

further instance, namely, the memorable earthquake of Lisbon, an

important phenomenon in the annals of Europe. Simultaneously with this

event, which took place on the 1st of November, 1755, not only were the

Lakes of Switzerland and the sea off the Swedish coasts violently

agitated, but in the eastern portion of the Antilles, near the islands

of Martinique, Antigua, and Barbadoes, the tide, which never exceeds

thirty inches, suddenly rose upwards of twenty feet. All these phenomena

prove, that subterranean forces are manifested either dynamically,

expansively, and attended by commotion, in earthquakes; or possess the

property of producing, or of chemically modifying substances in

volcanos; and they further show, that these forces are not seated near

the surface in the thin crust of the earth, but deep in the interior of

our planet, whence through fissures and unfilled veins they act

simultaneously at widely distant points of the earth’s surface.

The more varied the structure of volcanos, that is to say, of elevations

inclosing a channel through which the molten masses of the interior of

the earth reach the surface, the more important it is to form a correct

idea of these structures by careful measurement. The interest derived

from measurements of this kind, which I made a special subject of

inquiry in the western hemisphere, is increased by the consideration,

that the objects to be measured vary in magnitude at different points. A

philosophical study of nature seeks, in considering the changes of

phenomena, to connect the present with the past.

In order to ascertain the periodic recurrence, or the laws of the

progressive changes in nature, we require certain fixed points, and

carefully conducted observations, which, by their connection with

definite epochs, may serve as a basis for numerical comparisons. If the

mean temperature of the atmosphere and of the earth in different

latitudes, or the mean height of the barometer at the sea level, had

been determined only once in every thousand years, we should know to

what extent the heat of climates has increased or diminished, and

whether any changes have taken place in the height of the atmosphere.

Such points of comparison are especially required to determine the

inclination and declination of the magnetic needle, and the intensity of

those electro-magnetic forces on which Seebeck and Erman, two admirable

physicists belonging to this Academy, have thrown so much light. If it

be a meritorious undertaking on the part of learned societies to

investigate with perseverance the cosmical changes in the heat and

pressure of the atmosphere, and particularly the magnetic direction and

intensity, it is no less the duty of the travelling geologist to direct

attention to the varying height of volcanos in determining the

inequalities of the earth’s surface. The observations which I formerly

made in the Mexican mountains, at the volcano of Toluca, at

Popocatepetl, at the Cofre de Perote, or Nauhcampatepetl, and Xorullo,

and in the Andes of Quito at Pichincha, I have had opportunities since

my return to Europe of repeating, at different periods, on Mount

Vesuvius. Where complete trigonometric or barometric measurements are

wanting, their place may be supplied by angles of altitude laid down

with precision, and taken at points accurately determined. The

comparison of such determinations, made at different periods of time,

may sometimes be even preferable to the complication of more complete

operations.

Saussure measured Vesuvius in 1773, and at that time both the

north-western and south-eastern margins of the crater appeared to him to

be equal in height. He found their elevation above the level of the sea

to be 3894 feet. The eruption of 1794 occasioned a falling in towards

the south, and an inequality in the margins of the crater, which may be

distinguished from a considerable distance even by the most unpractised

eye. Leopold von Buch, Gay Lussac, and myself, measured Mount Vesuvius

three times in the year 1805, and found that the elevation of the

northern margin, la Rocca del Palo, opposite the Somma, was exactly as

it had been given by Saussure, while the southern margin was 479 feet

lower than it had been in 1773. The elevation of the volcano itself

towards Torre del Greco (the side towards which, for thirty years, the

volcanic action has been principally directed) had, at that time,

decreased one-eighth. The cone of cinders bears to the total height of

Vesuvius the relation of 1 : 3; in Pichincha, the ratio is as 1 : 10,

and at the Peak of Teneriffe, as 1 : 22. Of these three volcanic

mountains, Vesuvius has, therefore, comparatively, the highest cone of

cinders; probably because, being a volcano of inconsiderable height, it

has chiefly acted through its summit.

A few months ago, in the year 1822, I succeeded not only in repeating my

earlier barometric measurements of Mount Vesuvius, but also in

determining more completely all the margins of the crater[108] during

three ascents of the mountain.

These determinations are, perhaps, deserving of some degree of

attention, since they embrace the long period of the great eruptions

between 1805 and 1822, and are probably the only measurements hitherto

published of any volcano which admit of comparison in all their parts.

They prove, that the margins of the crater should be regarded as a much

more permanent phenomenon than has hitherto been supposed, from the

hasty observations made on the subject; and that this character

appertains to them everywhere, and not merely in those instances where,

as at the Peak of Teneriffe, and in all the volcanos of the Andes, they

evidently consist of trachyte. According to my latest determinations it

would seem, that since the time of Saussure, a period of forty-nine

years, the north-western margin of Vesuvius has probably not changed at

all, and that the south-eastern one, in the direction of Bosche Tre

Case, which in 1794 had become 426 feet lower, has since then only

altered about 64 feet.

If, in the newspaper reports of great eruptions, we often find

assertions made of an entire change of form in Mount Vesuvius, and if

these assertions appear to be confirmed by the picturesque views of the

volcano made at Naples, the cause of the error arises from the outlines

of the margins of the crater having been confounded with those of the

cones of eruption accidentally formed in its centre, the bottom of which

has been raised by the force of vapours. A cone of eruption of this

kind, formed by the accumulation of masses of rapilli and scoriæ,

gradually came to view, above the south-eastern margin of the crater,

between the years 1816 and 1818. The eruption in the month of February,

1822, increased this cone to such an elevation, that it projected from

107 to 117 feet above the north-western margin of the crater (the Rocca

del Palo). This remarkable cone, which was at length regarded at Naples

as the actual summit of Vesuvius, fell in with a fearful crash at the

last eruption, on the night of the 22nd of October; in consequence of

which, the bottom of the crater, which had continued uninterruptedly

accessible from the year 1811, is now nearly 800 feet below the northern

and 213 feet below the southern margin of the volcano. The varying form

and relative position of the cones of eruption, the apertures of which

must not, as they sometimes are, be confounded with the crater of the

volcano, give to Vesuvius at different epochs a peculiar physiognomy; so

much so, that the historiographer of this volcano, by a mere inspection

of Hackert’s landscapes in the Palace of Portici, might guess the exact

year in which the artist had made his sketch, by the outline of the

summit of the mountain, according as the northern or southern side is

represented in respect to height.

Twenty-four hours after the fall of the cone of scoriæ, which was 426

feet high, and when the small but numerous streams of lava had flowed

off, on the night between the 23rd and 24th of October, there began a

fiery eruption of ashes and rapilli, which continued uninterruptedly for

twelve days, but was most violent during the first four days. During

this period the explosions in the interior of the volcano were so loud

that the mere vibrations of the air caused the ceilings to crack in the

Palace of Portici, although no shocks of an earthquake were then or had

previously been experienced. A remarkable phenomenon was observed in the

neighbouring villages of Resina, Torre del Greco, Torre del’ Annunziata,

and Bosche Tre Case. Here the atmosphere was so completely saturated

with ashes that the whole region was enveloped in complete darkness

during many hours in the middle of the day. The inhabitants were obliged

to carry lanterns with them through the streets, as is often done in

Quito during the eruptions of Pichincha. Never had the flight of the

inhabitants been more general, for lava streams are less dreaded even

than an eruption of ashes, a phenomenon unknown here in any degree of

intensity, and one which fills the imaginations of men with images of

terror from the vague tradition of the manner in which Herculaneum,

Pompeii, and Stabiæ were destroyed.

The hot aqueous vapour which issued from the crater during the eruption,

and diffused itself through the atmosphere, formed, on cooling, a dense

cloud, which enveloped the column of ashes and fire, that rose to an

elevation of between 9000 and 10,000 feet above the level of the sea. So

sudden a condensation of vapour, and, as Gay Lussac has shown, the

formation of the cloud itself, tended to increase electric tension.

Flashes of forked lightning darted in all directions from the column of

ashes, while the rolling thunder might be clearly distinguished from the

deep rumbling sounds within the volcano. In no other eruption had the

play of the electric forces been so powerfully manifested as on this

occasion.

On the morning of the 26th of October the strange report was circulated

that a stream of boiling water was gushing from the crater, and pouring

down the cone of cinders. Monticelli, the zealous and learned observer

of the volcano, soon perceived that this erroneous report originated in

an optical illusion, and that the supposed stream of water was a great

quantity of dry ashes which issued like drift sand from a crevice in the

highest margin of the crater. The long drought, which had parched and

desolated the fields before this eruption of Vesuvius, was succeeded,

towards the termination of the phenomenon, by a continued and violent

rain, occasioned by the _volcanic storm_ which we have just described. A

similar phenomenon characterizes the termination of an eruption in all

zones of the earth. As the cone of cinders is usually wrapped in clouds

at this period, and as the rain is poured forth with most violence near

this portion of the volcano, streams of mud are generally observed to

descend from the sides in all directions. The terrified peasant looks

upon them as streams of water that rise from the interior of the volcano

and overflow the crater, while the deceived geologist believes that he

can recognise in them either sea-water or muddy products of the volcano,

the so-called _eruptions boueuses_, or, in the language of the old

French systematisers, products of an igneo-aqueous liquefaction.

Where, as is generally the case in the chain of the Andes, the summit of

the volcano penetrates beyond the snow-line, attaining sometimes an

elevation twice as great as that of Mount Etna, the inundations we have

described are rendered very frequent and destructive, owing to the

melting and permeating snow.

These are phenomena which have a meteorological connection with the

eruptions of volcanos, and are variously modified by the heights of the

mountains, the circumference of the summits which are perpetually

covered with snow, and the degree to which the walls of cinder cones

become heated; but they cannot be regarded in the light of true volcanic

phenomena. Subterranean lakes, communicating by various channels with

the mountain streams, are frequently formed in deep and vast cavities,

either on the declivity or at the base of volcanos. When the whole mass

of the volcano is powerfully shaken by those earthquakes which precede

all eruptions of fire in the Andes, the subterranean vaults open, and

pour forth streams of water, fishes, and tuffaceous mud. This singular

phenomenon brings to mind the _Pimelodes Cyclopum_, or the Silures of

the Cyclops, which the inhabitants of the plateau of Quito call

Preñadilla, and of which I gave a circumstantial account soon after my

return to Europe. When, on the night between the 19th and 20th of June,

1698, the summit of Mount Carguairazo, situated to the north of

Chimborazo, and having an elevation of more than 19,000 feet, fell in,

all the country for nearly 32 square miles was covered with mud and

fishes. A similar eruption of fish from the volcano of Imbaburu was

supposed to have caused the putrid fever, which, seven years before this

period, raged in the town of Ibarra.

I refer to these facts because they throw some light on the difference

between the eruption of dry ashes and mud-like inundations of tuff and

trass, investing fragments of wood, charcoal, and shells. The quantity

of ashes recently erupted from Mount Vesuvius, like every phenomenon

connected with volcanos and other great and fearful natural phenomena,

has been greatly exaggerated in the public papers; and two Neapolitan

chemists, Vicenzo Pepe and Guiseppe di Nobili, even asserted that the

cinders were mixed with given proportions of gold and silver,

notwithstanding the counter-statements of Monticelli and Covelli.

According to my researches the stratum of ashes which fell during the

twelve days was only three feet in thickness in the direction of Bosche

Tre Case, on the declivity of the cone, where they were mixed with

rapilli, while in the plains its greatest thickness did not exceed from

16 to 19 inches. Measurements of this kind must not be made at spots

where the ashes have been drifted by the wind, like snow or sand, or

where they have been accumulated in pulp-like heaps by means of water.

The times are passed in which, after the manner of the ancients, nothing

was regarded in volcanic phenomena save the marvellous, and when men

would believe, like Ctesias, that the ashes from Etna were borne as far

as the Indian peninsula. A portion of the Mexican gold and silver veins

is certainly found in trachytic porphyry, but in the ashes of Vesuvius

which I myself collected, and which were, at my request, examined by

that distinguished chemist Heinrich Rose, no trace of either gold or

silver was to be discovered.

However much these results, which perfectly correspond with the more

exact observations of Monticelli, may differ from those recently

announced, it cannot be denied that the eruption of ashes, which

continued from the 24th to the 28th of October, is the most memorable

that has been recorded, on unquestionable evidence, in reference to

Mount Vesuvius, since the death of the elder Pliny. The quantity of

ashes erupted on this occasion was probably three times as great as the

whole quantity which has fallen since volcanic phenomena have been

observed with attention in Italy. A stratum from 16 to 19 inches in

thickness does certainly, at first sight, seem very inconsiderable, when

compared with the mass with which we find Pompeii covered. But, without

taking into account the heavy rains and the inundations which must have

increased the bulk of this stratum in the course of ages, and without

reviving the animated contention maintained with much scepticism on the

other side of the Alps, regarding the causes of the destruction of the

Campanian cities, it may, at any rate, be here observed that the

eruptions of a volcano, at widely remote epochs, cannot be compared with

respect to their intensity. All conclusions must be insufficient that

are based on mere analogies of quantitative relations of the lava and

ashes, the height of the column of smoke, and the intensity of the

explosions.

We learn from the geographical description of Strabo, and from the

opinion expressed by Vitruvius on the volcanic origin of pumice, that,

until the year of Vespasian’s death, that is to say, until the eruption

which buried Pompeii, Vesuvius appeared more like an extinct volcano

than a Solfatara. When, after a long-continued repose, subterranean

forces suddenly opened for themselves new channels, penetrating through

strata of primitive rock and trachyte, effects must have been produced

to which no analogy is afforded by those of subsequent occurrence. We

clearly learn from the well-known letter in which Pliny the younger

informs Tacitus of the death of his uncle, that the renewal of the

eruptions, or, one might almost say, the revival of the slumbering

volcano, began with an outbreak of ashes. The same phenomenon was

observed at Xorullo, when the new volcano, in the month of September,

1759, breaking through strata of syenite and trachyte, was suddenly

upheaved in the plain. The country people fled in terror on finding

their cottages covered with ashes thrown up from the earth, which was

bursting in every direction. In the ordinary periodical manifestations

of volcanic activity a shower of ashes usually terminates each partial

eruption. The letter of the younger Pliny contains, moreover, a passage

which clearly shows that the dry ashes falling from the air immediately

attained a height of four or five feet, independent of accumulation by

drifts. “The court,” the narrative continues, “which led to the

apartment in which Pliny took his siesta, was so filled with ashes and

pumice that, had the sleeper tarried longer, he would have found the

passage wholly blocked up.” Within the inclosed limits of a court the

wind cannot have exercised any very considerable influence on the

drifting of the ashes.

I have interrupted my comparative view of volcanos by different

observations in relation to Vesuvius, partly on account of the great

interest excited by its recent eruption, and partly because every great

outpouring of ashes almost involuntarily recalls to mind the classic

soil of Pompeii and Herculaneum. In a note, not adapted to be read to

the audience to whom this lecture is addressed, I have collected all the

elements of the barometric measurements which I made during the close of

last year at Mount Vesuvius, and in the Campi Phlegræi.

We have hitherto considered the form and effects of those volcanos which

are permanently connected, by means of a crater, with the interior of

the earth. The summits of such volcanos are upheaved masses of trachyte

and lava intersected by numerous veins. The permanency of their effects

indicates a highly complex structure. They have, so to say, a certain

individuality of character, which remains unaltered for long periods of

time. Contiguous mountains generally yield wholly different products;

for instance: leucitic and feldspathic lavas, obsidian with pumice, and

basaltic masses containing olivine. They belong to the more recent

phenomena of the earth, usually breaking through all the strata of the

floetz formation, and their lava currents and products are of subsequent

origin to our valleys. Their life, if I may be permitted to use a

figurative expression, depends upon the mode and the duration of their

connection with the interior of the earth. After continuing for

centuries in a state of repose, their activity is often suddenly

revived, and they then become converted into Solfataras, emitting

aqueous vapours, gases, and acids. Occasionally, as at the Peak of

Teneriffe, their summits have already become a laboratory of regenerated

sulphur, while considerable lava currents, being basaltic near the base,

and mixed with obsidian and pumice at greater elevations, where the

pressure is less, continue to flow from the sides of the mountain[109].

Besides volcanos which have permanent craters, there is another kind of

volcanic phenomena less frequently observed than the former, but

especially instructive to the geologist, as they remind us of the

primitive world, that is, of the earliest revolutions of our planet.

Trachytic mountains suddenly open, and after throwing up ashes and lava,

close again never perhaps to re-open. Such has been the case with the

mighty volcano of Antisana in the chain of the Andes, and with Mount

Epomæus in Ischia, in the year 1302. Occasionally such an eruption has

occurred even in the plains, as on the table-land of Quito, in Iceland

at a distance from Hecla, and in the Lelantine plains of Eubœa. Many

upheaved islands belong to this class of transitory phenomena. In these

cases, the connection with the interior of the earth is not permanent,

the action ceasing as soon as the fissure, or channel of communication,

is again closed. Veins of basalt, dolerite, and porphyry, which traverse

almost all formations in different parts of the earth; and the masses of

syenite, augitic porphyry, and amygdaloid, which characterise the most

recent strata of transition rock, and the oldest stratum of the floetz

formation; have all probably been formed in a similar manner. In the

youthful period of our planet, the substances that had continued in a

fluid condition within the earth, broke through its crust, everywhere

intersected with fissures, and became solidified as granular veins, or

were spread out in broad superimposed strata. The products that may be

termed exclusively volcanic, which have come down to us from the

primitive ages of the world, have not flowed in streams or bands like

the lava of our isolated conical mountains. The mixtures of augite,

titanic iron, feldspar, and hornblende, may have been the same at

different periods, sometimes allied to basalt, sometimes to trachyte;

while chemical substances, (as we learn from Mitscherlich’s important

labours and the analogies presented by artificial igneous products,) may

have ranged themselves in layers according to some definite laws of

crystallization. In all cases we perceive that substances similarly

composed have come to the surface of the earth by very different means,

either by being simply upheaved, or escaping through temporary fissures;

and that breaking through the older rocks, that is to say, through the

earlier oxidized earth’s crust, they have flowed in the form of lava

streams from conical mountains having a permanent crater. If we do not

sufficiently distinguish between these various phenomena, our knowledge

of the geology of volcanos will again be shrouded in that obscurity,

from which numerous comparative experiments are now beginning gradually

to release it.

The questions have often been asked, what is it that burns in volcanos,

what generates the degree of heat capable of mixing earths and metals

together in a state of fusion? Modern chemistry has attempted to reply

that it is the earths, metals, and alkalies themselves, that is to say,

the metalloids of these substances, which burn. The solid and already

oxidized crust of the earth separates the surrounding atmosphere, with

the oxygen it contains, from the combustible unoxidized substances in

the interior of our planet. By the contact of these metalloids with the

atmospheric oxygen the disengagement of caloric ensues. The celebrated

and talented chemist, who advanced this explanation of volcanic

phenomena, soon himself relinquished it. The experiments which have been

made in mines and caverns in all parts of the earth, and which M. Arago

and myself have collected in a separate treatise, prove that even at an

inconsiderable depth, the temperature of the earth is much higher than

the mean temperature of the atmosphere at the same place. This

remarkable, and almost universally confirmed fact, is connected with

what we learn from volcanic phenomena. The depth at which we might

regard the earth as a fused mass, has been calculated. The primitive

cause of this subterranean heat is, as in all planets, the formative

process itself, the separation of the spherically conglomerating mass

from a cosmical aëriform fluid, and the cooling of the terrestrial

strata at different depths by the radiation of heat. All volcanic

phenomena are probably the result of a permanent or transient connection

between the interior and the exterior of our planet. Elastic vapours

press the fused oxidizing substances upwards through deep fissures.

Volcanos therefore are intermittent earth-springs, from which the fluid

mixtures of metals, alkalies, and earths, which become consolidated into

lava currents, flow gently and calmly, when being upheaved they find a

vent. In a similar manner, according to Plato’s Phædon, the ancients

regarded all volcanic streams of fire as effusions of the

Pyriphlegethon.

I would fain be permitted to add one yet bolder observation to those I

have already ventured to advance. May not the cause of one of the most

wonderful phenomena presented by the study of petrifactions, be

dependent on the condition of the inner heat of our planet, which is

indicated by thermometric experiments on springs[110] rising from

different depths, and by observations on volcanos? We find tropical

animals, arborescent ferns, palms, and bamboos, buried in the cold

north, and everywhere the primitive world presents a distribution of

organic structures wholly at variance with existing climatic relations.

Many hypotheses have been advanced in elucidation of so important a

problem, such as the approximation of a comet, the altered obliquity of

the ecliptic, and the increased intensity of the sun’s light; but none

of these have satisfied at once the astronomer, the physicist, and the

geologist. I, for my part, would willingly leave undisturbed the axis of

the earth or the light of the sun’s disk, (from whose spots a celebrated

astronomer explained fruitfulness and failure of crops,) yet it appears

to me that in every planet there exist, independently of its relations

to a central body and its astronomical position, numerous causes for the

development of heat, in processes of oxidation, in precipitation, in the

chemically altered capacity of bodies, the increase of electro-magnetic

tension, and in the channels of communication opened between its

internal and external parts.

Wherever, in the primitive world, heat was radiated from the deeply

fissured crust of the earth, palms, arborescent ferns, and all the

animals of the torrid zone, could perhaps have flourished for centuries

over extensive tracts of land. According to this view, which I have

already published in my work entitled _Geognostischer Versuch über die

Lagerung der Gebirgsarten in beiden Hemisphären_,[RG] the temperature of

volcanos would be that of the interior of our earth itself, and the same

causes which now occasion such fearfully devastating results, may have

been able to produce, in every zone, the most luxuriant vegetation on

the newly oxidized crust of the earth and on the deeply fissured strata

of rocks.

Should it be assumed, for the purpose of explaining the wonderful

distribution of tropical forms in their ancient mausolea, that the

long-haired elephantine animals, which are now found embedded in ice,

were once indigenous to northern latitudes, and that animals of similar

forms, belonging to the same type, as, for instance, lions and lynxes,

were capable of living in wholly different climates, such a mode of

explanation would at all events not admit of being extended to vegetable

products. From causes developed by the physiology of vegetation, palms,

bananas, and arborescent monocotyledons, are unable to endure the

deprivation of their appendicular organs, by the northern cold; and in

the geological problem which we are here considering, it seems to me a

matter of difficulty to admit any distinction between vegetable and

animal structures. One and the same mode of explanation must be applied

to both forms.

In concluding this treatise, I have added some uncertain and

hypothetical conjectures to the facts which have been collected in

widely remote regions of the earth. The philosophical study of nature

rises above the requirements of mere delineation, and does not consist

in the sterile accumulation of isolated facts. The active and inquiring

spirit of man may therefore be occasionally permitted to escape from the

present into the domain of the past, to conjecture that which cannot yet

be clearly determined, and thus to revel amid the ancient and

ever-recurring myths of geology.