I have sought in vain in the records of _Notes of a naturalist in South America

parts of the world for materials from which any probable inference may

be drawn as to a law regulating the ratio of decrease of temperature

with increasing height above the sea-level. There is reason to admit

that isolated peaks of no great height show a more rapid decrease

as compared with the plain than do considerable mountain masses. Of

mountains exceeding the height of 3000 metres in the tropics, the most

rapid rate of decrease is that recorded for Pangerango in Java, being

1° for 178·5 metres.

The greater mountain masses in or near the tropics show nearly the same

rate of decrement, by comparison with the sea-level, that I have been

led to infer from the observations in Ecuador. The average rate for

the Himalayas is about 1° for 194 metres of ascent, and for the less

lofty peaks of Mexico Humboldt’s observations show a decrease of 1°

for 188 metres. The great irregularities due to local conditions make

it impossible to derive any positive conclusions as to the comparative

rate of decrease in successive zones of elevation.

In Europe and North America comparisons between the temperatures at

mountain summits and the sea-level give rates of decrease varying

between 1° for 160 metres, and 1° for 170 metres; but it must be

remarked that the averages are mainly founded on observations made in

summer, and it is certain that the rate of decrease is much slower

in winter. Where the difference of height is not very great, it not

uncommonly happens that in winter the phenomenon is reversed, and that

we experience an increase of temperature in ascending above the plain.

The same result on a small scale may often be remarked on clear cold

nights, when the temperature rises for a distance of some hundred feet

in ascending isolated eminences, the effect being due to the cooling

effect of radiation from the surface.

It seems most probable that in the winter of the temperate and polar

zones the distribution of temperature in the atmosphere is subject to

conditions widely different from those prevailing in summer; and, if

that be true, we should have intermediate conditions in the spring

and autumn; so that even if we could arrive at comparatively accurate

results for one season of the year, these would not be applicable at

other periods.

The general result to which I have arrived is that to ascertain the

distribution of temperature in the atmosphere in successive zones

of elevation is a problem of extreme complexity, towards which the

existing materials do not furnish even an approximate solution. I

hold, however, that it ought to be possible to obtain much more

definite knowledge than we now possess by means of properly conducted

observations in various parts of the world.

Foremost of these I would suggest the importance of well-conducted

balloon ascents within the tropics. In selecting stations for such

ascents we are somewhat restricted by local considerations, especially

the extension of forests in many regions, such as the greater part

of tropical Brazil. In British India there would be no difficulty in

selecting suitable stations, and there would be additional value in

comparing the results obtained from ascents in Bengal, and in the

very different climate of the North-west Provinces. Elsewhere in the

tropics we might expect valuable results from ascents in Queensland,

and from the _llanos_ of Venezuela. It seems not impossible that, with

a considerably smaller outlay, useful results may hereafter be obtained

by means of improved self-recording instruments sent up in captive

balloons; but in most countries such a record would be liable to

interruption owing to storms.

The next desideratum is to obtain for a series of years simultaneous

observations at successive stations, at vertical intervals of 500 or

600 metres, situated on the flanks and at the summits of high mountains

to be chosen for the purpose. Some of these might with advantage be

chosen on islands, and among these the following may be suggested:--the

Peak of Teneriffe, Mauna Kea in the Sandwich Islands, Fusiyama in

Japan, the Piton de Neige in the island of Réunion, and Etna in Sicily.

It would add much to the value of these observations if in each case

there were a double series of stations, one series being on the

windward, the other on the leeward side of the mountain. It would also

be important to obtain observations at similar series of stations in

continental regions, removed from the immediate influence of the sea.

Pike’s Peak in Colorado, which already possesses an observing station

at the summit, and Mount Whitney in California, which Mr. Langley

has selected as eminently suited for an observatory, both offer many

advantages for the desired purpose. Another desirable station might

easily be found in the Caucasus, or in Armenia, and one or more could

be selected on the southern declivity of the Himalayas. In South

America, where railways have been carried to such great heights, it

may be hoped that regular observations may at some future time be

secured at the successive railway stations. It would be worthy of the

enlightened governments of Chili and Argentaria to make a commencement,

by providing for such a series being obtained at the stations on the

railway now in course of construction over the Uspallata Pass.

For the realization of most of these desires, as well as many others

affecting the progress of human knowledge, and the general welfare of

our race, we must be content to await the advent of a happier era, when

the fruits of industry, and the efforts of rulers, shall no longer

be mainly devoted to the maintenance and development of the arts of

destruction.

While awaiting such additional knowledge as may hereafter be obtained,

it is necessary in the mean time to form some provisional hypothesis

on which to base the formulæ for determining the difference of heights

of two stations, by barometric observations, and for ascertaining the

amount of atmospheric refraction; and the subject might with advantage

be discussed at a congress of scientific men. I have no authority

to decide on a question of such difficulty, nor do I pretend to be

thoroughly versed in the somewhat voluminous literature of the subject.

I may remark, however, that in one of the fullest and most elaborate

works by recent writers, Dr. Rühlmann[55] has proposed a formula for

the reduction of barometric observations which implicitly assumes

that the rate of decrement of temperature in ascending mountains is

uniform, inasmuch as he takes the mean of the temperatures observed at

the higher and lower stations as the value of the mean temperature of

the column of air between the two stations. It would appear that his

adoption of the hypothesis of an uniform rate of decrease is merely

due to the apparent impossibility of discovering a more satisfactory

hypothesis. Following on a line of inquiry first suggested by the

late M. Plantamour and M. Charles Martins, Dr. Rühlmann has analyzed

a series of two-hourly observations of temperature made during six

years at the hospice of the Great St. Bernard and at the Geneva

Observatory. Treating the mean temperature of the column of air between

the levels of those places as the unknown quantity, and neglecting,

as unimportant, the corrections for the tension of aqueous vapour and

for gravity, he has deduced the “true temperature,” as he styles it,

of the intermediate column from the equation of condition between the

pressures, the heights, and the temperatures of the two stations, for

the average of the two-hourly periods of observation for each month.

He has shown that, while on the average of the entire year the mean

“true temperature” of the intermediate column of air agrees pretty well

with the mean of the yearly observations at the two extreme stations,

the means for the separate hours and those for the separate months

usually differ widely from the so-called “true temperatures” for the

corresponding periods.

From this investigation Dr. Rühlmann has shown that during the warm

hours of the day, and the summer months, the “true mean temperature”

is lower than the mean of the observed temperatures at the two

extreme stations, while at night, and during winter, it exceeds that

mean to a rather greater extent. It may be objected that the cause

of the apparent discrepancy lies in the fact that, in thermometric

observations, we obtain, not the true temperature of the surrounding

air, but that of the thermometer, and that, however carefully

screened, the thermometer cannot be completely freed from the effects

of radiation to and from surrounding objects. This remark applies

especially to the observations at the St. Bernard, which lies at a

considerable distance from Geneva, and where the temperature is unduly

depressed by surrounding masses of snow. I do not, however, attach much

importance to these sources of error; and I have no doubt that under

the most favourable conditions the discrepancy shown by Rühlmann will

be found to a greater or less extent, but I differ from that writer in

the inference that he has drawn from the facts.

If I have not misunderstood his remarks, Dr. Rühlmann concludes

that the true temperature of the successive strata of air in the

zone between the base and the summit of a mountain is but slightly

affected by the diurnal changes that are exhibited in the range of the

thermometer, and to a moderate extent only by the changes of season as

shown by the range of the monthly means. He has not adverted to the

fact that the differences disclosed in his tables may be the result

of changes in the rate of decrement of temperature in ascending from

the lower to the higher station. He shows that, on the mean of the

July observations, the mean temperature of the air between the levels

of Geneva and the St. Bernard is lower than the mean difference of

the temperatures observed at those places by 1·57° C. But this is

not inconsistent with the supposition that the thermometers have

recorded the true air temperature at each station, but that the rate

of decrement of temperature in ascending, at that season, diminishes

rapidly in the successive vertical zones. In the same manner the fact

that the true mean temperature in January is higher than the mean

of the observed thermometers by 1·83° C., might be accounted for by

supposing that in winter the rate of decrement is smaller in the lower

strata, and increases in ascending above the surface. It is equally

true that, in both cases, the facts may be consistent with such an

irregular distribution of the atmosphere in successive layers, or

strata, of very unequal temperature as was apparent in most of Mr.

Glaisher’s balloon ascents. What is completely proved is that it is

only under exceptional conditions that the hypothesis of an uniform

rate of decrement of temperature, directly proportional to height

above the sea-level, is approximately correct for observations in the

temperate zone, where there is a considerable diurnal and annual range

of the thermometer.

My own impression, as the result of such study as I have been able to

give to the subject, is that, in the present state of our knowledge,

the reduction of barometric observations for the height of mountains

made by day, and in summer, in temperate latitudes, may best be

effected by the formula proposed by M. de St. Robert; while for

observations made at other seasons, and in the tropics, I should prefer

the formula proposed by Mr. Rühlmann.

Before closing these remarks, I may refer to an ingenious suggestion

made by M. de St. Robert in a paper published in the journal _Les

Mondes_ in Paris, in 1864, the substance of which is to be found in

the _Atti dell’ Academia delle Scienze di Torino_ for 1866, p. 193.

Impressed with the difficulty of approximating in practice to a correct

knowledge of the distribution of temperature in the air between the

summit of a mountain and a lower station, the author sought to escape

from it by seeking a phenomenon, susceptible of observation, which

should give a direct measure of the mean density of the air in the

space between the two stations. He pointed out that the velocity

of sound supplies such a measure, and that, given the barometric

pressures at the higher and lower stations, the angle of elevation of

the former, measured by a theodolite and corrected for refraction, and

the exact time required for sound to traverse the interval between

them, the height is given with a near approximation to accuracy by a

simple formula. The error arising from air currents, which increase or

diminish the velocity of transmission, would be readily eliminated by

discharging a fire-arm simultaneously at both stations, observing the

interval between the light reaching the eye and the report becoming

audible, and taking the mean of the intervals observed at both stations.

M. de St. Robert does not disguise the practical difficulty of

measuring the time interval with the requisite accuracy, but he thinks

that it may be obtained within a fifth of a second. The error in the

result is inversely proportionate to the time required to traverse the

distance, and where the stations are as distant as is compatible with

the sound being audible, its amount for an error of a fifth of a second

is inconsiderable.

This suggestion has not received the attention which it seems to

deserve. It possesses the advantage that the observations may readily

be repeated with little trouble or cost, and that the risk of error

may be much diminished by taking the mean of the observed intervals of

time. A comparison between observations between stations whose height

is known, made under different conditions, by day and night, and in

different states of weather, might, I think, contribute to diminish our

ignorance as to the variable conditions of the atmosphere at different

heights above the surface.

APPENDIX B.

REMARKS ON MR. CROLL’S THEORY OF SECULAR CHANGES OF THE EARTH’S CLIMATE.

Most scientific readers are familiar with the theory respecting the

influence of changes in the eccentricity of the earth’s orbit on the

climate of the globe, which has been sustained with remarkable ability

by Mr. James Croll. The views originally advanced in various scientific

periodicals were presented to the public in a connected form in the

volume entitled “Climate and Time,” wherein the author has brought a

wide knowledge of the principles of physics, and of the whole field of

geological science, to the support of his theory. Even those who have

not given especial attention to the subject are also acquainted with

the conclusions which Sir Charles Lyell drew from the discussion of Mr.

Croll’s arguments, and which are contained in the thirteenth chapter

of the tenth edition of his “Principles of Geology,” and also with the

more recent examination of the subject which is to be found in Mr.

Alfred Wallace’s important work, “Island Life.”

I need not say that a theory so important in its bearing on some of the

most obscure problems of geology has been discussed, in more or less

detail, by many other writers. To most of the objections presented to

his theory, Mr. Croll has replied with his usual ability; and I believe

that at present the prevailing tendency among geologists is towards a

partial acceptance of his views, subject to the limitations assigned

by Mr. Wallace. The latter author holds, in common with Sir Charles

Lyell, that geographical causes, arising from the varying distribution

of land and sea, have mainly controlled the distribution of temperature

over the earth’s surface; but he is disposed to go farther than Lyell

in admitting the influence of periods of high eccentricity in causing

those great accumulations of snow and ice which were requisite to

produce the phenomena of a glacial period, whenever a sufficient area

of elevated land in high latitudes coincided with the period of high

eccentricity.

It would probably be of little avail, even if I were to undertake the

task, that I should attempt any thorough discussion of this vast and

difficult problem; and it would certainly require far more space than

can here be given to it. I may, however, venture to make a few remarks

upon some points which have not, to the best of my knowledge, been much

noticed in the discussion.

In reading Mr. Croll’s work, which charmed many an hour during the

voyage to and from South America, I found it very difficult to discover

any flaw in the chain of close reasoning by which he supports his

conclusions. Most of the facts on which he relies are warranted by

observation, and have been accepted as well established by writers of

the highest authority; and his inferences as to the results of altered

conditions appeared to be in strict conformity with admitted physical

principles. Nevertheless, when I reflected on the anomalies which are

found at the present time in respect to the climate of many spots in

the world, and the complexity of the causes which determine its actual

condition, I felt a doubt whether, in his attempt to trace the result

of possible changes, Mr. Croll may not have overlooked some of the

elements of the problem.

Let me briefly state the leading propositions of Mr. Croll’s theory in

order to make intelligible the succeeding remarks.

Estimating approximately the mean distance of the earth from the sun

at ninety-one and a half millions of miles, and the eccentricity[56]

of the sun’s place in the orbit at one and a half million, it follows

that at one period of the year, which happens to be about the winter

solstice of the northern hemisphere, the earth receives from the

sun a quantity of heat greater than that which reaches it in the

opposite part of its orbit, in the proportion of 93^2 to 90^2, or

about as 1000 to 936. Midsummer of the southern hemisphere is the

season when the earth is nearest to the sun; the winter of the southern

and the summer of the northern hemisphere occur when the earth is

farthest from the source of heat. The conclusion seems inevitable--the

southern hemisphere must have hotter summers and colder winters than

our hemisphere, where the heat of summer is tempered by the greater

distance, and the cold of winter mitigated by the comparative nearness,

of the sun.

The next point to be considered is the effect of ocean-currents, and

especially of the Gulf-stream, in modifying the climatal conditions of

some parts of the earth. Following in the track of the late Captain

Maury and Principal Forbes, Mr. Croll has especially insisted on

the importance of the great current which, issuing from the Gulf

of Mexico, and flowing northward between Florida and the Bahamas,

extends across the Atlantic towards the western shores of Europe. He

calculates that by this current alone an amount of heat equal to that

received on the entire surface of the earth in a zone thirty-two miles

in breadth on each side of the equator is carried from the tropics

to the cooler regions of the northern hemisphere. Mr. Croll has, I

think, victoriously replied to several of the objections opposed to

this portion of his argument. His estimate of the volume of water

transferred by the Gulf-stream from the tropics to the northern part of

the Atlantic, which he reckons at the annual amount of about 166,000

cubic miles, is, I think, in no degree exaggerated; and I also think

that he is warranted in estimating the mean initial temperature at

about 65° Fahr. I am, however, persuaded that in assuming 40° Fahr.

as the temperature to which, on an average, this vast body of water

is reduced before it returns to the equatorial zone, Mr. Croll has

gone beyond the probable limit. A large part of the stream is diverted

eastward about the latitude of the Azores, and is never cooled much

below 55° Fahr. before the waters enter the return current on the

eastern side of the Atlantic basin; and I believe that, if we allow the

water of the Gulf-stream to undergo an average loss of temperature of

20° Fahr., we shall be more likely to exaggerate than to underrate the

amount of cooling.

In insisting on the importance of the Gulf-stream in modifying the

climate of Europe and the adjacent parts of the arctic zone, Mr. Croll

agrees with many preceding writers; but, so far as I know, he was the

first to suggest that in consequence of the greater persistency of the

south-east trade-winds, which ordinarily extend up to, and, at some

seasons, even north of, the equator, the warm waters of the Northern

Atlantic derive a large share of the heat which is carried to the

temperate and arctic zones from the southern hemisphere. Applying the

same reasoning to the currents of the Pacific Ocean, Mr. Croll arrives

at the general conclusion (“Climate and Time,” p. 94) that “the amount

of heat transferred from the southern hemisphere to the northern is

equal to all the heat falling within fifty-two miles on each side of

the equator.”

I do not believe that the facts on which Mr. Croll bases this essential

portion of his theory are sufficiently established. With regard to the

Atlantic, I have expressed in the text (p. 344) an opinion, derived

from conversations with practical seamen, that in the Atlantic the

trade-winds of the northern are stronger than those of the southern

hemisphere. That opinion, I am disposed, on further examination, to

regard as incorrect. I believe that the north-east trade-winds often

blow with greater force; but, taking the average of the entire year, I

now think there can be no doubt that the south-east trade-winds extend

over a wider area in the equatorial zone. However this may be, our

knowledge of the currents of the Atlantic does not, I think, authorize

us to conclude that the portion of heated water carried from the

southern to the northern hemisphere is nearly so large as Mr. Croll has

estimated. If the heat of the Gulf-stream were mainly supplied, as Mr.

Croll contends, from that source, there should be a marked difference

in the volume and temperature of the current, between the season when

the north-east trade-winds approach the equator and that in which the

south-east trades prevail to the north of the line, for which there is

no evidence.

As regards the currents and winds of the Pacific, in spite of one

considerable exception, to which I shall further allude, I think

that the balance of evidence points to a greater prevalence of the

south-east trade-winds, and to the probable transference of some

portion of the equatorial waters from the southern to the northern

hemisphere.

For the present discussion it is best to accept Mr. Croll’s estimate,

and to compare the amount of heat which he supposes to be transferred

from one hemisphere to the other with the total amount which is

received annually from the sun on each hemisphere. For this purpose

I have taken the known areas of the torrid, temperate, and frigid

zones respectively, and, following Mr. Croll, I have adopted Mr.

Meech’s estimate of the average amount of heat, per unit of surface,

received from the sun in each zone, irrespective of absorption by the

atmosphere. To estimate the proportion of heat which actually reaches

the surface, I have adopted Pouillet’s measure of the proportion of

solar radiation cut off at vertical incidence, which is 24 per cent. I

assume 28 per cent. to be the average loss in the torrid zone, 50 per

cent. in the temperate zone, and 75 per cent. in the frigid zone.[57]

The resulting figures, showing the proportional amount of heat annually

received on the surface of each zone, and on the entire hemisphere, are

as follows:--

Torrid zone 3370

Temperate zone 2304

Frigid zone 112

----

Whole hemisphere 5786

Calculating, on the same basis, the amount received on a zone one mile

wide at the equator, allowing a loss of 25 per cent. from atmospheric

absorption, and multiplying the result by 104, I obtain the number

233·1 or rather more than one twenty-fifth part of the entire heat

annually received from the sun by each hemisphere.

To trace the results of such a transfer of heat from one hemisphere to

the other, I shall adopt a mode of reasoning, sanctioned by the great

authority of Sir John Herschel, to which Mr. Croll frequently resorts.

It is by solar heat that the surface of the earth is raised above the

temperature of space, which is assumed to be 239 degrees below the

zero of Fahrenheit’s scale. Adopting Ferrel’s estimate, I take the

mean temperature of the northern hemisphere at 59·5° Fahr., or 298½

degrees above the temperature of space. To maintain this temperature,

it receives one-half of the amount of solar radiation which reaches

the earth, and in addition, on Mr. Croll’s hypothesis, one twenty-fifth

part of that which reaches the southern hemisphere. It follows that the

heat available to raise the southern hemisphere above the temperature

of space stands to that which is received by the northern hemisphere

in the ratio of 24:26, and that the mean temperature of the southern

hemisphere should be 298·5 × 12/13, or 275·5° above the temperature

of space; so that, in ordinary language, the mean temperature of the

southern hemisphere should be 36·5° Fahr. If the fact corresponded with

this result of theory, it would not be necessary to invoke increased

eccentricity of the earth’s orbit to account for the extreme cold of

one hemisphere, seeing that the actual conditions would suffice to

completely alter their relative temperatures.

It occurs to me, however, that, on further consideration, Mr. Croll

would reduce his estimate of the volume of heated water transferred

from the southern to the northern hemisphere; but even if that estimate

were reduced by one-half, we ought to find in the southern hemisphere a

mean temperature of 47·8° Fahr., or nearly 12 degrees lower than that

of our hemisphere.

We have already seen that, so far as climate depends on the relative

position of the earth and the sun, we ought to find in the southern

hemisphere climates of a more extreme character, with hotter summers

and colder winters, than those to which we are accustomed. If it be

true that through the agency of ocean-currents a considerable amount

of heat is transferred to the northern hemisphere, that circumstance

might serve to account for the fact that the summers of the southern

are not generally hotter than those of the northern hemisphere; but it

would, at the same time, tend to aggravate the severity of the southern

winters.

At the time of the publication of Mr. Croll’s earlier memoirs, there

existed a general belief that the southern hemisphere was in fact

notably cooler than our portion of the globe, and he naturally referred

to the supposed fact as harmonizing with the general conclusions drawn

by him from theory. But, imperfect as our knowledge of the southern

hemisphere still is, a good deal of information has been obtained of

late years. The only stations south of the fiftieth degree of latitude

from which we possess continuous observations are those mentioned

in the text (p. 273); but we also know with sufficient accuracy the

climates of two widely separated islands lying about 50° south; and

from these we derive results widely different from those to which we

were led by theoretical considerations. The following table gives

approximately the mean temperatures, on Fahrenheit’s scale, for the

year and for the hottest and coldest months of the places referred to

in the southern hemisphere, and the means for corresponding latitudes

in the northern hemisphere:--

Key:

A: S. latitude.

B: Temperature of January.

C: Temperature of July.

D: Mean of year.

E: N. hemisphere. July.

F: N. hemisphere. January.

G: N. hemisphere. Yearly mean.

--------------------------+-------+-----+-----+-----+-----+-----+-----

| A | B | C | D | E | F | G

--------------------------+-------+-----+-----+-----+-----+-----+-----

Kerguelen Land |49° 17’|44·3°|35·3°|39·6°|63·3°|22·0°|42·9°

Auckland Island |50° 30’|50·2°|35·6°|44·6°|62·3 |19·0°|41·1°

Falklands (Stanley) I.[58]|51° 41’|49·6°|36·5°|43·0°|61·6°|17·1°|39·8°

Falklands II. |52° 5’ |55·9°|37·4°|47·3°|61·3°|16·4°|39·3°

and II. | |52·7°|37·0°|45·1°|61·5°|16·7°|39·6°

Punta Arenas |53° 25’|51·4°|34·7°|43·0°|60·6°|14·2°|37·7°

Ushuaia[59] |54° 53’|53·2°|31·8°|41·9°|59·6°|12·0°|36·2°

--------------------------+-------+-----+-----+-----+-----+-----+-----

If we compare the mean results of these five stations with those for

corresponding latitudes in the northern hemisphere, we find that the

summers are cooler and the winters very much milder, and that in the

latitudes between 50° and 55° the mean annual temperature is notably

higher. In Kerguelen Land alone the mean annual temperature is lower

than the normal for the same latitude north of the equator; but that

island is evidently exposed to exceptional conditions.

The differences between the mean results given above are shown by the

following table, in which the signs show the excess or deficiency of

the southern as compared with the northern hemisphere:--

Warmest month. Coldest month. Annual mean.

-11·1° Fahr. +18·1° Fahr. +4·2° Fahr.

Dr. Hann has carefully discussed the question as to the comparative

mean temperatures of the two hemispheres in a paper published in the

proceedings of the Vienna Academy, the substance of which is given in

his _Klimatologie_, pp. 89, _et seq._; and it is difficult to refuse

assent to his conclusion that so far as the available evidence goes, it

shows that the mean temperature of both hemispheres is equal.

I find, then, that the same train of reasoning by which Mr. Croll has

sought to explain the occurrence of glacial periods by changes in the

eccentricity of the earth’s orbit, and the precession of the equinoxes,

leads us to conclusions respecting the climatal condition of the

different parts of the earth, at the present amount of eccentricity,

which are altogether opposed to the results of observation; and I am

driven to the conclusion that the causes which he has adduced have

not the predominant influence which he has attributed to them, and

that there must be other agencies to which he has not assigned their

due importance, but which are adequate to counteract the efficiency

of those which, as observation proves, fail to achieve the effects

anticipated from them.

I am far from pretending to be able to analyze completely the complex

agencies which, by their mutual action, determine the climate of

different parts of the earth, but I may briefly refer to two of them.

Foremost of these is the relative distribution of land and sea, for

a due appreciation of which we are indebted to the great work of Sir

Charles Lyell. It is unnecessary here to discuss how far his view of

the probable amount of change in past geological epochs may, in the

present state of our knowledge, be subject to limitation. Mr. Wallace,

who is the most strenuous supporter of the modern doctrine of the

permanence of the present continents and ocean basins, recognizes the

theoretical correctness of Lyell’s views, and admits that changes of

level great enough to cause profound modifications of climate have

actually occurred. Notwithstanding recent objections, it appears to me

that Darwin’s hypothesis as to the subsidence of a great tract in the

Southern Pacific is that which best accounts for the existence of the

countless coral islands in that region; nor is the probability of a

nearly continuous barrier of volcanic islands across the Atlantic to be

completely dismissed. That such changes would have largely affected the

climate of the earth cannot, I think, be doubted.

If I may venture to express my own view on this difficult subject, I

must say that, although it has not been overlooked by the able men

who have discussed it, the paramount importance of aqueous vapour as

an agent for modifying climate has not yet been fully recognized. Mr.

Croll has constantly discussed the phenomena of ocean-currents, as if

their chief function were to affect climate by heating or cooling the

surrounding air, which is thence diffused over the land surfaces, and

he has devoted little attention to the effects of evaporation from

the sea, and the subsequent condensation in some other region of the

vapour produced. When we remember that as much heat is consumed in

the conversion of one cubic mile of water into vapour as would raise

the temperature of nearly ninety-seven cubic miles of water by 10°

Fahr., we get some measure of the vast power of vapour as a vehicle of

heat. Admitting, as I am disposed to do, that 166,000 cubic miles of

water are annually conveyed northward by the Gulf-stream, and suffer

an average loss of 20° Fahr. before returning to the torrid zone, I

must point out that the entire heat requisite to maintain this great

volume of water at the higher temperature would be consumed in the

conversion of 3433 cubic miles of water into vapour. In point of fact,

I believe that more than one-half of the quantity specified is expended

in evaporation, and that the cooling of the waters of the Gulf-stream

is mainly due to this agency. To follow the vapour thus produced, to

ascertain where it is condensed, and where the heat disengaged in the

act of condensation becomes available to raise the temperature of the

air, is a task which is beyond our present resources; but it is one

which must be performed before we can reason with any confidence as

to the ultimate distribution of the heat carried by the Gulf-stream

or any other ocean-current. Whatever part of the vapour produced by

evaporation from the Gulf-stream goes to supply the rainfall of

Western Europe, or to form snow in the arctic regions, acts as a

vehicle to transfer heat from the tropics to the temperate and frigid

zones. But it is more than probable that a large part of the vapour

in question is carried back to the torrid zone, and that some of it

is even restored to the southern hemisphere. The south-eastern branch

of the Gulf-stream flows, at least partially, into the area of the

north-east trade-winds. These winds reach the lower region as cold and

very dry winds. As they advance towards the equator, and are gradually

warmed, their capacity for aqueous vapour constantly increases, and

there can be no doubt that in both hemispheres the trade-winds bear

with them a large share of the vapour which goes to supply the heavy

rainfall of the tropics.

In the Pacific region we have direct evidence to this effect, in the

fact that in Hawaii, and elsewhere, the side of the islands exposed to

the trade-winds is that of heavy rainfall, and is generally covered

with forest. No sufficient data exist for estimating the amount

of vapour thus carried back to the tropics from high latitudes on

both sides of the equator, nor the amount of heat set free by its

condensation; but we may form some conception of its probable amount by

considering that at the moderate estimate of a mean annual rainfall of

seventy-two inches for the portion of the globe between the tropics,

this amounts to a yearly fall of 88,737 cubic miles, and that we can

scarcely reckon the share of this great volume of water supplied by

evaporation from the same part of the globe at more than one-half.

Still less is it possible to calculate the amount of vapour annually

transferred from the northern to the southern hemisphere, which goes

to neutralize the apparent effect of the diversion of portions of the

equatorial waters to the north side of the line. In the Atlantic basin

it is probable that the larger part of the rainfall in the region

including and surrounding the Gulf of Mexico and the Caribbean Sea is

supplied by vapour carried from the temperate zone by the north-east

trade-winds. There is some reason to believe that a portion of the

rainfall of the great basin of the Amazons, south of the line, is also

supplied from the same source. Several travellers report that during

the rainy season the prevailing winds are from the west and north-west,

the latter being especially predominant at Iquitos, about 4° S.

latitude, and 1600 miles from the mouth of the river.

In tropical Australia the rainy season falls during the prevalence

of the north-west monsoon, and we cannot doubt that this is mainly

supplied by vapour carried from the northern hemisphere. Another

region wherein the same phenomenon is exhibited on a large scale is

the central portion of Polynesia, extending from the Feejee to the

Society Islands over a space of at least twenty degrees of longitude.

Over that wide area, as far as about twenty degrees south of the line,

the regular south-east trade-wind prevails only in the winter of the

southern hemisphere, while during the rest of the year, especially in

summer, north and north-east winds have the predominance. Taking the

mean of three stations in the Feejee Islands, of which the returns are

given by Dr. Hann, I find in round numbers the very large amount of 150

inches for the mean annual rainfall, of which 105 fall during the seven

months from October to April, while the five colder months from May to

September supply only forty-five inches of rain. There can be little

doubt that the larger part of the 105 inches falling during the warm

season is derived from the northern hemisphere.

I by no means seek to account fully for the apparent contradiction

between the results of theory, as developed by Dr. Croll, and the

actual distribution of heat over the earth as proved by observation;

but I venture to think that I have shown reason to doubt the

possibility of drawing absolute conclusions as to the results of

astronomical changes until we shall have fuller knowledge than we now

possess of all the agencies that regulate climates.

Before concluding these remarks, I will notice one other branch of the

argument in regard to which I am unable to concur with Mr. Croll. As we

have seen, the essential point in his theory as to the _modus operandi_

of changes of eccentricity, and the relative position of the poles, on

the distribution of temperature, is that the currents of the equatorial

zone are driven towards the pole which has the summer in aphelion,

and that the cause of this shifting of the currents depends on the

greater strength of the trade-winds in the hemisphere which has the

winter in aphelion; the strength of the trade-winds in turn depending

on the amount of difference of temperature between the equatorial

and the colder zones. Taking the surface of the earth generally, the

trade-winds of the southern are probably stronger than those of the

northern hemisphere, and, if it were true that the south temperate and

frigid zones were colder than those of the other hemisphere, it would

be allowable to argue that the greater difference of temperature as

compared with the equatorial zone was the cause of the greater strength

of the trade-winds. But we now certainly know that the southern

hemisphere between latitudes 45° and 55° is considerably warmer than

the corresponding zone of the northern hemisphere, and we have good

grounds for believing that the mean temperature of the whole hemisphere

south of latitude 45° is higher, and certainly not lower, than that

of the same portion of the northern hemisphere. We are therefore

not justified in explaining the greater strength of the southern

trade-winds by a greater inequality of temperature between the equator

and the pole.

In my opinion the cause of this predominance of the southern

trade-winds is to be sought in the fact that the southern is mainly

a water hemisphere, while the northern is in great part a land

hemisphere. In the south, the great currents of the atmosphere flow

with scarcely any interruption, except that caused by Australia, where,

in fact, the trade-winds are irregular, and lose their force. In the

northern hemisphere the various winds originating in the unequal

heating of the land surface interfere with the normal force of the

trade-winds, and weaken their effect.

In connection with this branch of the subject, I may remark that the

belief in the greater cold of the southern hemisphere mainly rests

on the fact that all the land hitherto seen in high latitudes has

been mountainous, and is covered by great accumulations of snow and

ice. But this does not in itself justify the conclusion that the mean

temperature is extremely low. It is true that the fogs which ordinarily

rest on a snow-covered surface much diminish the effect of solar

radiation during the summer in high latitudes, but this is compensated

by the great amount of heat liberated in the condensation of vapour.

The only part of the earth which is now believed to be covered with

an ice-sheet is Greenland, but the mean of the observations in that

country shows a temperature higher by at least 10° Fahr. than that of

Northern Asia, where the amount of snowfall is very slight, and rapidly

disappears during the short arctic summer. If there be, as some persons

believe, a large tract of continental land surrounding the south pole,

I should expect to find that the great accumulations of snow and ice

are confined to the coast regions. In that case the mean temperature of

the region within the antarctic circle would probably be lower than it

would be in the supposition, which appears to me more probable, that

the lands hitherto seen belong to scattered mountainous islands. If,

from any combination of causes, one pole of the earth has ever been

brought to a mean temperature much lower than that now experienced,

I should expect to find that the phenomena of glaciation would be

exhibited towards the equatorial limit of the cold zone, rather than

in the portions near the pole. The formation of land-ice depends on

the condensation of vapour, and before air-currents could reach the

centre of an area of extreme cold the contained vapour would have been

condensed. This consideration alone suffices, to my mind, to make the

supposition of a polar ice-cap in the highest degree improbable.

Mr. Wallace (“Island Life,” p. 142) cites, as conclusive evidence of

the effect of winter in aphelion in producing glaciation, the facts,

to which attention was first directed by Darwin, as to the depression

of the line of perpetual snow, and the consequent extension of great

glaciers, on the west coast of Southern Chili. I have adverted to

this subject in the text (p. 229), and I may further remark that if

winter in aphelion be the cause of the depression of the snow-line in

latitude 41° S., it can scarcely fail to produce some similar effect

in latitude 34° S. Yet we find on the southern limit the snow-line

much lower, and at the northern much higher, than it has ever been

observed in corresponding latitudes in the northern hemisphere, the

line being depressed by more than 8000 feet within a distance of only

seven degrees of latitude. The explanation, as I have ventured to

maintain, is altogether to be found in the extraordinary rainfall of

Southern Chili; and to the same cause we must attribute the fact that,

in spite of the greater distance of the sun, the winter temperature is

higher than in most places in corresponding latitudes in the northern

hemisphere. At Ancud in Chiloe, in latitude 41° 46′, the temperature

of the coldest month is lower by less than three and a half degrees

of Fahrenheit than it is at Coimbra in Portugal, one and a half degree

nearer the equator, in the region which receives the full warming

effect of the Gulf-stream.

I should have expressed myself ill in the preceding pages if I should

be supposed to deny that, in his writings on this subject, Mr. Croll

has made an important contribution to the physics of geology. He has,

in my humble opinion, been the first to recognize the full importance

of one of the agencies which, under possible conditions, may have

profoundly affected the climate of the globe during past epochs,

although I do not believe that, in the present state of our knowledge,

we can safely draw those positive inferences at which he has arrived.

Even those who are unable to accept any portion of his theory as to the

causes of past changes of climate must feel indebted to his writings

for numerous valuable suggestions, and for the removal of many popular

opinions which his acute criticism has shown to be untenable.

INDEX.

_Acacia Cavenia_, 157

Aconcagua, 192

---- valley, vegetation of, 195

_Adesmia_, 182

Agassiz, Professor Alexander, 342

Ajulla, Promontory of, 51

Albatross, 215

Alligators, 41

Alpine zone in Andes, 91

Amancais, 71

Amatapi, Sierra, 52

Ancud, 145

Andean Flora, Alpine zone, 104

----, divisions of the, 104

----, European genera common to, 101

Andean railways, 63

Andes, 49

----, Alpine zone in, 91

----, cactoid plant in, 92

----, Chilian, view of, 183

----, climate of Peruvian, 99

----, _Compositæ_ in, 102

----, cosmopolitan weeds in, 101

Aneroid barometers, 353, 354

Angol, 213

Antarctic beech, 256

---- Flora, range of, 219

_Anthopterus Wardii_, 34

Anticosti, 273

Apoquinto, baths of, 188

Araucanian Indians, 212

----, language of, 213

_Araucaria Brasiliensis_, 311

Argentaria, climate of, 300

----, emigration to, 298, 299

----, forests of, 295

----, progress of agriculture, 298

----, frontier of Chili and, 258

Arica, vegetation of, 121

_Armeria maritima_, var. _andina_, 263

Artichoke, wild, 168

Atacama, desert of, 124, 131

Atlantic, colour of, 7

----, summer temperature of, 362

----, temperature of, 5

----, winds of, 345

_Ayacucho_ steamship, 118

Azores, 5

_Baccharis_, 157

Bahia Blanca, 298, 357, 358

Bahia de Todos Santos, 346

_Baillonia spartioides_, 202

Balmacedo, Don F., 191

Banda Oriental, 281

----, vegetation of, 293

Barbadoes, absence of venomous snakes in, 14

----, black population of, 11

---- harbour police, 9

---- planters, 13

----, productiveness of, 8

Barometer, high, 4

----, tables for, 4

Beagle Channel, 273

Belem, Tower of, 363

_Berberis buxifolia_, 263

---- _empetrifolia_, 263

---- _ilicifolia_, 263

Berberry, 225

Bentos, Fray, 287

Bio-Bio river, 213

Black-fish, 7

Blue Mountains, Jamaica, 17

_Bombax pubescens_, 328

Borya Bay, 241

Bossi, Signor Bartolomeo, 281

Botafogo, 322

Bove, Lieutenant, 252

Bramble in Chili, 150

Brazil, ancient mountains of, 317

----, coffee-planting in, 341

----, geology of, 313, 314

----, glacial deposits in, 342

----, rainfall in coast region of, 334

Brazilian physicians, their fees, 340

Bridges, suspension, in the Andes, 85

Buenaventura, 32

Buenos Ayres, 293-295, 299

Cabo Blanco, 43

---- San Lorenzo, 37

---- Santa Elena, 38

Cachapoal river, 178

Cactoid plant in Andes, 92

Caldera, 133

Callao, 61

----, quarantine at, 57

Canary Islands, 362

Cape Froward, 243

---- Parinas, 44

---- pigeon (_Daption capensis_), 214

---- Pillar, 238

---- Verde Islands, 359

Capricorn, Tropic of, 132

Cardoon, 164

Casapalta, 91

Catamarans, 352

_Cathartes atratus_, 112

Caudivilla, 109

Cauquenes, Morro de, 182

----, town of, 169

Cauquenes Baths, 172

----, railway to, 163

Celery, wild, 221

_Cereus Quisco_, 151, 176

Cerro de Pasco, 72

---- del Roble, 151

Chacao, Canal de, 216

Chagres river, 22

Chañeral, 133

Channels of Patagonia, 222, 223

Chicla, hotel at, 80

----, scenery at, 84

----, vegetation of, 98

Chili and Argentaria, frontier of, 258

---- and Peru, naval war of, 58

----, bramble in, 150

----, Central, flora of, 141

---- ----, climate of, 143-145

---- ----, rainfall in, 144

----, European plants in, 164

----, physical geography of, 170

----, Southern, glaciers of, 229

---- ----, rainfall of, 229

Chilian elections, cumulative vote, 191

---- mines, 161

_Chiliotrichium amelloides_, 234

Chiloe, island of, 215

Chimborazo, 38

Chonos Archipelago, 216

Chosica, 73

_Chuquiraga spinosa_, 91

Churches in Lima, 62

_Chusquea_, 152

Cigars, Guayaquil, 41

Cinnamon tree, 10

Claraz, M. Georges, 357, 358

Clarence Island, 243

Climate, effects of tropical, 39

_Cnicus lanceolatus_, 164

Cobeja, 131

Coffee-planting in Brazil, 341

_Colletia spinosa_, 177

Colomba, 214

Colon, 21, 22, 27

Commercial travellers, German, 309

_Compositæ_ in Andes, 102

Concepcion del Uruguay, 288

Condor, 87, 93

Condors, captive, 185

Copiapò, 133

----, Rio de, 133

Coquimbo, vegetation of, 136, 138

Corbett, Mr., 328

Cordillera de la Costa, 218

Cordillera Grande, of Goyaz, 315

Cordillera Pelada, 218, 219

Cordillera in Peru, 49

Corrientes, 294, 300

Cosmos Line, German steamers of, 205

Cousiño, Madame, 207

Crab, red, 227

Croll, Dr. James, 271

----, remarks on his theory of secular changes of climate, 393

_Cryptocarya Peumus_, 160

Cuyabà, 279, 310

Dandelion (_Taraxacum lævigatum_), 263

_Daption capensis_, 214

Darwin, Mount, 267, 270

Dawson Island, 245

_Desfontainea spinosa_, 225

Desolation, Land of, 235, 241

_Diomedea exulans_, 215

---- _fuliginosa_, 215

_Don_, Royal Mail steamer, 2

_Doterel_, wreck of the, 267

_Drimys Winteri_, 147

Drummond-Hay, Mr., 148

Dungeness, 271

_Duvaua dependens_, 293

Earthquake-waves, 122

_Eccremocarpus scaber_, 199

Ecuador, 36, 40

Eden harbour, 224

Education, Chilian zeal for, 265

Elections, Chilian, cumulative vote, 191

_Encelia canescens_, 134

Engler, Dr., 34, 106

English Narrows, 223

English the _lingua franca_ of America, 88

Ensenada, 302

Entrerios, 288

Equator, cold current near, 356

----, path of the sun, 37

Equatorial rains, 352

---- vegetation, 33

_Erodium cicutarium_, 165

_Escallonia_, 181

Espiritu Santo, Cape, 271

_Eucalyptus globulus_, 160, 292

Evergreen beech (_Fagus betuloides_), 225

Existence, struggle for, 330

Eyre Sound, 228

_Fagus betuloides_, 225

---- _obliqua_, 151

Falkland Islands, 247, 273

Fayrer, Sir Joseph, 349

Fenton, Dr., 250, 262, 269

Fernando Noronha, 354, 355

Feuillée, Father, 184

Flint, Mr., 153

Flowering plants, origin of, 318

Flying-fish, 5

---- of Pacific, 53

Fogs on Peruvian coast, 54

_Francoa sonchifolia_, 210

French, Dr., 289, 291

Fruit-sellers, migratory, 42

Fuegians, 233, 242, 260, 261

Gallinazo, 87

----, scavenger bird, 112

_Galvesia limensis_, 45

Gillies, Captain, 344

Glacial deposits in Brazil, 342

Glaciers in South Patagonia, 239

---- of Southern Chili, 229

Glaziou, Dr., 324

_Gleichenia_, 226, 311

_Glyptodon_, 358

Gongo Seco, 316

Gordontown, Jamaica, 18

----, cool climate of, 19

Graham, Mr. J. R., 67

Granite, disintegration of, 315

Grisebach, 34, 145

Gualtro, 168

Guanacos, 131, 253

Guano Islands, 53

Guayaquil cigars, 41

Guayaquil, city of, 40, 41

----, Gulf of, 38, 40

Guayas river, 38, 41, 42

_Gynopleura linearifolia_, 157

Hale Cove, 220

Hann, Dr. Julius, 144, 305, 349

Hanover Island, 236

Hayti, island of, 15

----, cannibalism in, 16

Haze, opacity of, 158

Heights above sea-level, fall of temperature in ascending to, 369

Henderson’s Inlet, 231

Hess, Mr., 163

_Hippeastrum equestre_, 19

Hopedale, in Labrador, 273

Huanillos, 127

Humboldt current, 50

Humming-birds, 209

_Hura crepitans_, 10

_Hymenophylla_, 226

_Iberia_ steamship, 269

Ice-axe, 226

Ice, floating, 228

Illiluk, 274

Immigrant plants, Darwin’s view of, 166

----, checks on their extension, 167

Indians, Araucanian, 212

----, Patagonian, 260

Iquique, 121

----, sea-fight at, 127

Isla de Santa Maria, 211

_Islay_ steamship, 29

Itamariti, Falls of, 329

Jamaica, 16

----, black population of, 20

----, vegetation of, 18

Jacmel harbour, 15

_Kageneckia oblonga_, 175

Kingston, Jamaica, 16

_Lapageria rosea_, 209

La Plata, estuary of, 277, 283

Las Condes, 163

La Serena, 136, 145

Lavapie Promontory, 211

Liais, M., 342

_Libocedrus_, 235

Lichens, 221

Lima, 61

----, a dinner-party at, 108

----, ancient beaches near, 113

----, meteorological observations at, 99

_Liriodendron_, 344

Lisbon, Rock of, 363

Llaillai, 150

Llama in Peru, 95

Loa river, 127

_Lobelia gigantea_, 184

_Lobelia tupa_, 184

----, poisonous species of, 76

Lobos de tierra, 53

---- de afuera, 53

_Lomaria magellanica_, 226

Lombardi, Signor M., 109

Lombardy poplar, 160

_Loranthus_, 176, 202

Lord Nelson Strait, 236

Lota, coal deposits of, 207

----, parque of, 208

Lynch, Don Patricio, 67

----, his administration, 68

Maceio, 347

Magellan, Straits of, 238, 239, 367

----, forests in the, 240

----, variable climate in, 240, 254

Maipo river, 134

Maldonado, 304

_Malesherbiaceæ_, 157

Mango tree, 10

Mapocho river, 157

Markham, Captain Albert, 135

_Marrubium vulgare_, 138

Matto Grosso, 279

Matucana, San Juan de, 76

Mayne Channel, 237

_Maytenus magellanica_, 263

Meiggs, Mr., 65

Mejillones, 132

Memory, lapses of, 26

Mendoza, 300

Mercator’s projection, 30

Messier’s Channel, 220, 231

Mist, clearing of, 333

_Mitraria coccinea_, 225

Molina, 175

Mollendo, 119

----, a bad port, 120

Monkeys, domesticated, 332

Monson, Mr., 280

Montaña of Eastern Peru, 97

Monte Video, 277, 279

Morro de Cauquenes, 182

Mountain-sickness, 81

_Mulinum_, 189

_Mutisia_, 177

_Mutisiaceæ_, 102

_Myzodendron punctulatum_, 256

Napp, Mr. Richard, 300

Nation, Mr. W., 70, 108

Naval war of Chili and Peru, 58

New Granada, 32

_Nicotiana glauca_, 360

Nikolaiewsk, 273

North Atlantic, trade-wind of, 361

Northern hemisphere, temperature of, 273, 274

O’Higgins, General, 154

Olfactory nerve, fugitive impressions, 190

_Oreodoxa regia_, 324

Organ Mountains, 325

Oroya railway, 64

----, spiral tunnel of, 79

----, viaducts of, 74

Ostrich, South American, 261

_Oxalis lobata_, 146

Pacific coast-steamers, 31

Pacific, colour of water of, 31

----, first view of, 25

----, flying-fish of, 53

----, high seas in Southern, 211

---- steamer, delay of, 269

Paisandu, 288, 289

Palms, avenue of, 323

Panama, 21

---- Bay, birds in, 29

---- Grand Hotel, 27

---- railway, 25

---- ship-canal, 23

----, vegetation of, 24

Paraguay river-steamers, 279

Paranà, 317

----, basin of the, 312

---- river, 284

Paranagua, Bay of, 308

Paranahyba, 313

---- valley, 320

Parasites and climbers, 330

Patagonia, 300

---- Channels, scenery of, 222, 227

----, vegetation of, 225, 235

----, women of, 253

Patagonian coast, winter climate, 276

Patagonian Indians, 260

Payta, climate and vegetation of, 45

Peckett Harbour, 262, 270

Pedro, Dom, Emperor of Brazil, 337

Pelicans, black, 59

Peñas, Gulf of, 218

Pernambuco, 351

_Pernettya_, 225

Peru, 44

---- and Chili, naval war of, 58

----, climate of Northern, 47

----, future of, 117

Peruvian coast, fogs on, 54

----, low temperature of, 55

---- sugar-plantation, 110

Pessimism, 365, 366

Petrel, giant, 215

Petropolis, 326, 327, 335

----, hermit of, 331

----, winter climate of, 334

Peumo tree, 159, 175

Philippi, Dr., 154

----, Professor Federigo, 155, 219

Physicians, Brazilian, their fees, 340

Pierola, Dictator of Peru, 117

Pietrabona, Commander, 257

Pimento tree, 10

Pisagua, 123

----, white rocks at, 125

Pisco, 119

_Plantago maritima_, 263

_Pleroma arboreum_, 342

---- _granulosum_, 336

_Podocarpus nubigena_, 235

Poncho, 179

_Porliera hygrometrica_, 199

Port Famine, 245, 250

---- Gallant, 241

Potato, wild, in Andes, 93

Prado, General, 36

_Prosopis limensis_, 46

_Proustia Baccharoides_, 195

_Pteris aquilina_, 329

Puente Infernillo, 78

Puerto Bueno, 233

Punta Arenas, 145, 246, 273

_Puya_, 151

Quadras in Santiago, 153

Quarantine at Callao, 57

---- at St. Vincent, 359

_Quaresma_, 336

Queen Adelaide Island, 236, 238

_Quillaja saponaria_, 175

Quillota, Valley of, 150

Quinta Normal at Santiago, 155

Railways, Andean, 63

----, Oroya, 64

----, spiral tunnel of, 79

----, viaducts of, 74

Rancagua, 168

Reed, Mr. Edwin, 204

Reilly, Mr., 210

Resguardo del Rio Colorado, 200

_Rhamses_, the, 205

_Rhea Darwinii_, habits of, 261

Rimac, valley of the, 71

----, ancient terraces in, 75

----, _Compositæ_ in, 76

----, effects of sea-breeze in, 98

Rio Claro, 171

---- Colorado, 276

---- Janeiro, Bay of, 321, 322, 325

---- Parahyba do Sul, 313

---- San Francisco, 314

Rocks, disintegration of, 115

----, ice-action on, 228

_Rumex acetosella_, 263

_Sagittaria Montevidensis_, 297

Saladeros, 287

_Salix Humboldtiana_, 77

Salta, 294

Salto, 291

_Sambucus Peruviana_, 101

Sampayo, Don Francisco, 257

San Bartolomé, 73

---- Cristobal, Cerro, 156

Sand-box tree (_Hura crepitans_), 10

Sandy Point, 246, 250

----, burnt forest at, 256

----, mutiny of convicts at, 251

----, the hotel at, 249

----, vegetation of, 255, 263

San Felipe, 192

Sanitary rules, neglect of, 87

San José, Promontory of, 276

---- volcano, 164

San Lorenzo, island of, 59

San Matias, Bay of, 276

San Paulo, 308-310

---- and Rio Janeiro railway, 312

----, railway from Santos to, 307, 308

San Ramon, Salto de, 190

Santa Clara, 72

Santa Cruz settlement, 246

Santa Lucia, Rock of, 162

Santa Rosa de los Andes, 193, 196

Santiago, 145, 153, 156, 161

----, railway to, 149

----, sunset at, 186

Santos, 305, 306

----, tropical vegetation at, 307

São João da Barra, 312

São Salvador, 346

Sarmiento Channel, 231

Sarmiento, Mount, 243, 244, 267, 270

Scavenger bird, 112

_Schinus molle_, 77

Sea-sickness, 217

Seaweed, bands of, 6

_Senecio_, the genus, 268

Serra da Mantiqueira, 313, 314

Serra do Mar, 308, 314

Shannon, Captain, 269

Simpson, Captain, 207

Sitka, 274

Smyth’s Channel, 231, 237

_Solanum mammosum_, 33

Soroche, mountain-sickness, 81

Soto, Don Olegario, 171

South America, tropical, origin of flora, 35

----, rainless zone of, 48

South Brazil, plateau of, flora, 311

South Patagonia, glaciers in, 239

Southern Atlantic, climate of, 305

Southern Cross, 7, 253

Southern hemisphere, temperature of, 272-274

Spanish-Americans, indolence of, 89

Species, groups of incomplete, 181

Staten Island, 252, 258

St. Antão Island, 359

Steamers, Pacific coast, 31

Straits of Magellan, 270

Sunstroke, causes of, 349, 350

Surco station, 75

Swinburne, Don Carlos, 154

Taforò, Dr., 191

_Tagus_ steamship, 344

Talca, 145

Taltal, 133

Tamar, Cape, 240

Tambo de Mora, 119

Tarapacà, 125

_Taraxacum lævigatum_, 263

Telephone, use of, in South America, 290

Tierra del Fuego, 245, 267

Tijuca, 338

----, giant tree near, 343

----, vegetation of, 341

_Tillandsia_, 307

Titicaca, Lake of, 63, 66

Tocantins river, 315

Tocopilla, 128, 133

----, scenery of the moon, 129

Trade wind, north-east, 6

Trescott, Mr., 60

Tres Montes, Cape, 218

Trinidad, Gulf of, 231

_Triumph_, the ship, 135

_Tropæolum tuberosum_, 78

Trumpet-flower (_Bignonia venusta_), 307, 311

Tucuman, 294

Tumaco, 36

Tumbez, 43

_Tupa Berterii_, 184

---- _secunda_, 184

Tupungato, the Peak of, 153

Ucayali river, English settler at, 96

Unalaschka, 274

Uruguay, climate of, 279

----, fossil remains in, 291

----, islands of the, 287

---- Republic of, chronic disorder, 282, 284, 285

Ushuaia, mission station at, 260

Ushuaja, 273

Uspallata Pass, 200

_Utricularia_, 33

Valdivia, 145

Valparaiso, 138, 145

----, danger of earthquakes at, 139

Vegetation, equatorial, 33

Verbena family, 201

Viaducts, Oroya railway, 74

Vicuña Mackenna, Don Benjamin, 158

Villages, remains of ancient Peruvian, 73

Viña del Mar, 149

Vincent, St., aspect of, 360

----, quarantine at, 359

Vinciguerra, Signor, 252

Virgenes, Cape, 271

Volcano de Chana, 219

Wellington Island, 222

Willsen, Captain, 205

Winter’s bark (_Drimys Winteri_), 147

Yellow fever, treatment of, 339

NOTE ON THE MAP OF SOUTH AMERICA.

In the annexed map an attempt has been made to represent the probable

course of the isothermal lines--lines denoting equal temperature--in

the South American continent. The black lines indicate the mean

temperature for the entire year; the red lines that for January, the

hottest month; and the green lines that of July, the coldest month.

The numbers placed over each line in corresponding colours indicate

the temperature in degrees of the Centigrade scale. We possess a fair

amount of information as to the meteorology of the coasts of the

continent; but of the interior our knowledge is miserably deficient,

and is nearly limited to several stations in Argentaria, and a few in

the basin of the Amazons. As a result, the course of the isothermal

lines in the interior is to a great extent conjectural. As in all

similar maps, no account has been taken of the relief of the surface;

when a line crosses a mountain range, the temperature indicated is

that which would be found, as is assumed, if the height were reduced

to the sea-level. No attempt has been made to show the variations of

temperature with the season in the part of the continent near the

equator. These are very slight, and depend mainly on local conditions,

the mean temperature of the year varying from 25·5° to 28° C., or from

about 78° to 82° Fahr.; the hottest seasons near the equator, apart

from local conditions, being those of the equinoxes.

The chief interest of the map to the physical geographer arises from

the remarkable effect of the southern, or Humboldt, current, in

lowering the temperature of the western coast between the fifth and the

fortieth degrees of south latitude. This is, of course, most apparent

in the isothermal for January. It will be seen that at that season the

temperature of Northern Peru is about the same as that of Buenos Ayres,

lying thirty degrees farther from the equator. In mid-winter (July)

the effect is far less apparent, and in the south of the continent

the isotherms for that season nearly correspond with the parallels of

latitude. The lines indicating mean annual temperature naturally assume

a course intermediate between those for the extreme seasons.

PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, LONDON AND BECCLES.

[Illustration:

Edw^{d.} Weller, lith.

_London: Kegan Paul, Trench & Co._

SOUTH AMERICA

illustrating the

NOTES OF A NATURALIST.

]

FOOTNOTES

[1] For a list of the plants collected here, see a paper in the

_Journal of the Linnæan Society_, vol. xxii.

[2] Much cinchona bark, coming from the interior, was formerly shipped

at Tumaco; but between horrible roads and the reckless waste of the

forests through mismanagement, but little is now conveyed by this way.

[3] For a list of the species collected, see the _Journal of Linnæan

Society_, vol. xxii.

[4] The abrupt change in the vegetation on this part of the American

coast has been noticed by Humboldt, Weddell, and other scientific

travellers. In a note to the French edition of Grisebach (“Vegetation

du Globe,” traduit par P. de Tchihatcheff, ii. p. 615), M. André

expresses the opinion that this, as well as some other cases of abrupt

change in the vegetation observed by him in Colombia, are to be

explained by the nature of the soil, which in the arid tracts is sandy

or stony, and fails to retain moisture. Admitting that in certain cases

this may afford a partial explanation of the facts, it is scarcely

conceivable that the limit of the zone wherein little or no rain falls

should exactly coincide with a change in the constitution of the soil,

and I should be more disposed to admit a reversed order of causation,

the porous and mobile superficial crust remaining in those tracts

where, owing to deficient rainfall, there is no formation of vegetable

mould, and no accumulation of the finer sediment forming a retentive

clay.

[5] The only detailed account of the operations that I have seen is in

a work entitled, “Histoire de la Guerre du Pacifique,” by Don Diego

Barros Arana. Paris: 1881. It appears to be fairly accurate as to

facts, but coloured by very decided Chilian sympathies.

[6] The heights given in the text are those of the railway stations.

[7] Of 138 genera of _Helianthoïdeæ_ 107 are exclusively confined to

the American continent, 18 more are common to America and distant

regions of the earth, one only is limited to tropical Asia, and

two to tropical Africa, the remainder being scattered among remote

islands--the Sandwich group, the Galapagos, Madagascar, and St. Helena.

[8] See note to page 184.

[9] In _Nature_ for September 14, 1882.

[10] The only accurate information that I have found respecting the

climate of Lima is contained in a paper by Rouand y Paz Soldan,

“Resumen de las Observaciones Meteorologicas hechas en Lima durante

1869,” quoted in the French translation of Grisebach’s “Vegetation du

Globe.” Reduced to English measures, they give the following results:--

Mean temperature of four years 66·6° Fahr.

” ” January, 1869 74·3° ”

” ” July, 1869 57·6° ”

Rainfall in the year 1869 13·4 inches.

” June, 1869 2·45 ”

” July, 1869 2·72 ”

” August, 1869 2·48 ”

” September, 1869 2·33 ”

” October, 1869 2·16 ”

” remaining seven months 1·24 ”

There is reason to think that the temperature for July, 1869, given

above was exceptionally low, and although the months during which fogs

prevail are abnormally cool for a place within 13° of the equator, I

believe that the thermometer rarely falls below 60° Fahr.

[11] See Appendix A, On the Fall of Temperature in ascending to Heights

above the Sea-level.

[12] It is a curious illustration of the utterly untrustworthy

character of statements made by unscientific travellers to read the

following passage in a book published by a recent traveller in South

America, who visited Chicla in November, the beginning of summer. He

declares that the fringe of green vegetation “dwindles and withers at

a height of nine or ten thousand feet;... while on the upper grounds,

where sometimes rain is plentiful, the air is too keen and cold for

even the most dwarfish and stunted vegetation to thrive.”

[13] “Versuch einer Entwicklungsgeschichte der Pflanzenwelt.”

[14] The heights are certainly incorrect. The base of the hill of

Amancaes is nearly seven hundred feet above sea-level, and Mr. Nation

states that the two localities mentioned by Mr. Cruikshank are at about

the same elevation.

[15] Two small Chilian wooden ships, the _Esmeralda_, of 850 tons,

mounting eight guns, commanded by Arturo Prat, and the _Covadonga_,

of 412 tons, with two guns, commanded by Condell, were engaged in the

blockade of Iquique, when, on the 21st of May, 1879, they were attacked

by the Peruvian ironclad _Independencia_, of 2004 tons, mounting 18

(chiefly heavy Armstrong) guns, commanded by J. G. Moore, and the

monitor _Huascar_, of 1130 tons, mounting two 300-pounder Armstrong

turret guns, besides two deck guns, under Miguel Grau, the most skilful

and enterprising of the Peruvian commanders. The Chilian captains

resolved on a desperate defence. After maintaining for two hours the

fight against the _Huascar_, Arturo Prat resolved on the attempt to

board his adversary. Bringing his ship alongside, he sprang on the deck

of the _Huascar_; but the ships were separated at once, and two men

only fell along with him, while the _Esmeralda_ went to the bottom with

her crew of 180 men, of whom several were picked up by the boats of

the _Huascar_. The _Independencia_, following the little _Covadonga_,

ran on the rocks in the shallows south of Iquique, and became a total

wreck; while the _Covadonga_, though shattered by her enemy’s guns, was

able to reach Autofogasta. The heroism of the Chilian commanders saved

their country, and at the critical moment changed the fortune of the

war.

[16] In the preface to his “Florula Atacamensis,” Dr. Philippi, who has

explored this region more thoroughly than any other traveller, states

that on the range of coast hills between the Pan de Azucar (lat. 26° 8′

south) and Miguel Diaz (lat. 24° 36′) the fogs, called in Peru _garua_,

or _garruga_, deposit during a great part of the year some moisture

which occasionally takes the form of fine rain, such as is familiarly

known to occur on the hills near Lima. He remarks as singular the fact

that the same phenomenon is not observed on the coast north or south of

those limits. From more recent observations, it would appear that this

is not strictly true as regards the higher coast hills near Coquimbo,

but it seems to hold as regards the tract of coast to the northward,

between the neighbourhood of Taltal and that of Iquique, a distance

of about four degrees of latitude. It may be that the coast hills are

lower here than further south, and that as the desert region inland

rises very gradually, and has a higher temperature inland than near the

coast, the formation of fog is prevented. Whatever be the cause, the

absence of fog would go far to account for the utter sterility of this

region.

[17] The four species of _Encelia_ described in De Candolle’s

“Prodromus” appear to me to be but slightly modified forms of a single

species. Since the publication of that work, several other and quite

distinct species have been ranked under the same generic name.

[18] While botanizing in the Tajo de Ronda, the singular cleft which

cuts through the rocky hill on which the town is built, I was once for

some time in positive danger. The boys, having espied me, assembled on

the bridge that crosses the cleft, some three hundred feet above my

head, and commenced a regular fire of stones, that drove me to take

shelter under an overhanging rock until, being tired of the sport, they

turned their attentions elsewhere.

[19] One of the difficulties felt by all students of geographical

distribution arises from the imperfect or careless indications given

both in books and in herbaria, and this is more felt in regard to South

America than as to any other part of the world. A very large proportion

of the earlier collections bear simply the label “Brazil,” forgetting

that the area is as great as that of Europe. In other cases local

names of places, not to be found on maps or in gazetteers, embarrass

the student and weary his patience. It is mainly from Darwin that

naturalists have learned that geographical distribution is the chief

key to the past history of the earth.

[20] The last season of excessive rainfall was that of 1877. I have

seen no complete returns, but it appears that the rain of that year

commenced in Central Chili in February, a very rare phenomenon; that

more than six inches of rain fell in April, of which, at Santiago,

four inches fell in twenty-four hours. More heavy rain fell in May,

and finally in July a succession of storms flooded large districts,

destroying property and life, the fall for the month being more than

fourteen inches at Valparaiso. Much interesting information respecting

the climate of Chili will be found in a work by Don B. Vicuña Mackenna,

“Ensayo Historico sobre el Clima de Chile” (Valparaiso: 1877), from

which I have borrowed the above-mentioned particulars.

[21] I believe that in the column for rainfall at Punta Arenas, snow

has not been taken into account.

[22] The recent untimely death of this valuable official is deplored by

all classes in Chili.

[23] This is doubtless the summit described by Darwin under the name

Campana de Quillota. He gives the height as 6400 feet above sea-level.

The figures in the text are taken from the Chilian survey.

[24] The mapping of the Andean chain is a task of immense difficulty,

and although the Chilian survey is the best that has yet been executed,

it leaves much to be desired. Even in the small district which I was

able to visit, I found several grave errors in Petermann’s map, reduced

from the Chilian survey, which is, nevertheless, the best that has

been published in Europe. One of the most serious is the omission of

the Uspallata Pass, the most frequented of those leading from Central

Chili to the Argentine territory, which is neither named nor correctly

indicated by the tints adopted to mark the zones of elevation.

[25] “Origin of Species,” 3rd edit., p. 410.

[26] Molina, one of the most pernicious blunderers who have brought

confusion into natural history, grouped together under the generic name

_Peumus_ several Chilian plants having no natural connection with each

other. Misled by his erroneous description, botanists have applied

the name _peumus_ to a fragrant shrub, common about Valparaiso and

elsewhere, which is known in the country by the name _boldu_.

[27] The Baths of Cauquenes are said to be 2523 feet above the sea; the

_Morro_, by aneroid observation, is about 2000 feet higher.

[28] As happens with many other plants described by early botanists,

there has been much confusion in regard to the species named by

Linnæus _Lobelia Tupa_. The plant was first made known to Europeans

by the excellent traveller, Father Feuillée, whose “Journal des

Observations Physiques Mathématiques et Botaniques faites sur les

côtes de l’Amérique meridionale, etc.,” published in 1714, is a book

which may still be consulted with advantage. His descriptions of

plants are usually careful and accurate, but the accompanying plates

all ill-executed and often misleading. Linnæus, followed by Willdenow,

refers to Feuillée’s work, but gives a very brief descriptive

phrase which suits equally well Feuillée’s plant and several others

subsequently discovered. Aiton, in the “Hortus Kewensis,” gives the

name _Lobelia Tupa_ to a plant which is plentiful about Valparaiso,

where I found it still in flower, the seeds of which were received at

Kew about a century ago from Menzies. This is now generally known by

the not very appropriate name _Tupa salicifolia_ of Don, but was first

published by Sims in the _Botanical Magazine_, No. 1325, as _Lobelia

gigantea_, which name it should now bear. The plant which I found near

Cauquenes appears to be the _Tupa Berterii_ of Decaudolle, a rare

species, apparently not known to the authors of the “Flora Chilena.”

No doubt could have arisen as to the plant intended by Linnæus as

_Lobelia Tupa_ if writers had referred to Feuillée’s full and accurate

description. His account of the poisonous effects of the plant was

probably derived from the Indians, and may be exaggerated. The whole

plant, he says, is most poisonous, the mere smell causing vomiting,

and any one touching his eyes after handling the leaves is seized

with blindness. I may remark that the latter statement, which appears

highly improbable, receives some confirmation from the observations

of Mr. Nation, mentioned above in page 77. The plant which I saw in

Peru, but failed to collect, is much smaller than most of the Chilian

species, and has purple flowers, but is nearly allied in structure. It

is probably the _Tupa secunda_ of Don. I gather from a passage in one

of Mr. Philippi’s writings that the word _tupa_ in Araucanian signifies

poison. We are yet, I believe, ignorant of the chemical nature of the

poisonous principle contained in the plants of this group.

[29] The measurements of the height of the peak of Aconcagua vary

considerably in amount, but I believe that the most reliable is that

adopted by Petermann--6834 metres, or 22,422 English feet.

[30] The inconvenience of using a periphrasis for the name of so

important a country may warrant my adoption of the obvious name

Argentaria in place of Argentine territory, or Argentine Confederation,

and I shall adhere to the shorter designation in the following pages.

[31] It is quite possible that the bird which I took for the black

albatross was the giant petrel, common, according to Darwin, in these

waters, and closely resembling an albatross.

[32] See an interesting paper in the _Journal of Botany_ for July, 1884.

[33] The estimates given by Pissis do not rest on accurate

observations, and seem to me exaggerated. I should be inclined to

reckon the difference of height of the snow-line between the extreme

stations as nearer to two thousand than to three thousand feet.

[34] I am not aware that the concurrent conclusions as to the height

of this mountain have been verified by accurate observations, but the

height commonly given appears to be a close approximation to the truth.

[35] “Flora Antarctica,” vol. ii. p. 289.

[36] See Appendix B.

[37] It is unfortunate that the Spaniards who had the naming of so

large a part of the American continent should have shown so little

inventive faculty. When they did not adopt a native name for a river,

they rarely got beyond Red River, Black River, or Big River, and

wherever we turn we encounter a Rio Colorado, a Rio Negro, or a Rio

Grande.

[38] The constant inconvenience of employing such cumbrous expressions

as Argentine Confederation or Argentine territory for a state of such

vast extent and such yearly increasing importance must be felt by every

one who has occasion to speak or write about this region of America. I

trust that I shall be forgiven if in this book, as well as elsewhere,

I have taken the liberty of applying a single name, which has nothing

about it so strange as that it should not long since have come into use.

[39] The Paranà, with its great tributary the Paraguay, drains an

area of more than 1,100,000 square miles; the basin of the Uruguay is

reckoned at 153,000 square miles.

[40] The term _provinces_, commonly applied to the federated States, is

misleading, and should be laid aside.

[41] Much information respecting this country is to be found in a

volume entitled, “The Argentine Republic,” published in 1876 for the

Centenary Exhibition at Philadelphia. It contains a series of papers

prepared by Mr. Richard Napp, assisted by several German men of science.

[42] Dr. Hann (“Klimatologie,” p. 657, _et seq._) has discussed the

causes of the prevalent high barometric pressure on both coasts of

temperate South America, and has shown that in winter the area of

maximum pressure moves northward towards the Tropic of Capricorn.

[43] The species common here is allied to _T. stricta_, but is not, I

think, identical.

[44] The best general account of the geology of Brazil that I have seen

is contained in a short paper by Orville A. Derby, entitled, “Physical

Geography and Geology of Brazil.” It was published in the _Rio News_,

in December, 1884, and, through the kindness of Mr. Geikie, i have seen

a reprint in the library of the School of Mines.

[45] _Proceedings of the Royal Geographical Society_ for 1879, p. 564.

[46] See his valuable work, “Climats, Géologie, Faune et Géographie

Botanique du Bresil.”

[47] “Klimatologie,” p. 382.

[48] Darwin’s estimate of the height was one thousand feet, while

Professor Moseley gives double that amount. I incline to think that the

lower figure is nearer to the truth.

[49] I borrow this statement from the excellent “Lehrbuch der

Klimatologie,” by Dr. Julius Hann. Stuttgart, 1883.

[50] See _Reports of the British Association for the Advancement of

Science_ for 1882, pp. 451-453.

[51] It is remarkable that there is no reference to the investigations

of M. de St. Robert, and the formula deduced from them, in the article

on the “Barometrical Measurement of Heights,” in the new edition of the

_Encyclopædia Britannica_.

[52] Published by the War Department, United States Army, _Professional

Papers of the Signal Service_, No. xv.

[53] Air nearly saturated with vapour is lighter than air relatively

dry; and hence it may happen that, when a current of moist air meets

one relatively dry, it will flow over the latter if they are nearly at

the same temperature, but if the drier current be much warmer, it may

flow beneath it.

[54] On this subject see _Handbuch der Klimatologie_, by Julius

Hann, pp. 141, _et seq._ See also Tables I. and II. in a report on

thermometric observations in the Alps, by J. Ball, in _Reports of the

British Association for the Advancement of Science_ for 1862, pp.

366-368.

[55] See “Die Barometrischen Höhenmessungen und ihre Bedeutung für die

Physik der Atmosphäre,” Leipzig, 1870, by R. Rühlmann.

[56] I use the term “eccentricity” in the popular sense, to express the

distance of the focus from the centre of the ellipse.

[57] Viewed in the light of Mr. Langley’s recent researches on solar

radiation, all these numerical determinations are probably far from the

truth; but the errors do not much affect the present argument.

[58] The observations at Stanley Harbour, which are those adopted by

Dr. Hann (_Klimatologie_, p. 697), show temperatures notably lower than

those recorded for a place in the islands lying farther south, which

are given in the _Zeitschrift der Œsterreichischen Gesellschaft für

Meteorologie_, vol. v. p. 369. The mean of the two is probably nearly

correct.

[59] These figures are derived from the tables given in the _Anales de

la Oficina Meteorologica Argentina_, by B. Gould, vol. iii. The figures

show a considerable amount of annual variation. The monthly means of

the six months from February to July, 1879, exceed those of the same

period in 1878 by more than 2° Fahr.

Transcriber’s Notes

Punctuation, hyphenation, and spelling were made consistent when a

predominant preference was found in this book; otherwise they were not

changed.

Simple typographical errors were corrected; occasional unbalanced

quotation marks retained.

Ambiguous hyphens at the ends of lines were retained.

Index not checked for proper alphabetization or correct page references.

Page 4: “30·40” was misprinted as “39·40”.

I have sought in vain in the records of mountain observations in other