lives in liberty in our climate. As its name indicates, it prefers
to frequent the walls of old buildings and finds a refuge in the
interstices, hollowing out the mortar half disintegrated by time. The
entrance to the dwelling is protected by a tube curved toward the
bottom, and making an external prominence. The owner comes and goes
by this passage, and as it is curved toward the earth the interior is
protected against a flow of rain, while at the same time the entry is
rendered more difficult for Melectes and Anthrax. These insects, in
fact, watch the departure of the Anthophora to endeavor to penetrate
into their nests and lay their eggs there. The gallery of entry and
exit has been built with grains of sand, the débris produced by the
insect in working. These grains of sand glued together form, on
drying, a very resistant wall.
The other animals of which I have to speak are genuine masons, who
prepare their mortar by tempering moistened earth. Every one has
seen the swallow in spring working at its nest in the corner of a
window. It usually establishes its dwelling in an angle, so that the
three existing walls can be utilized, and to have an inclosed space
there is need only to add the face. It usually gives to this the form
of a quarter of a sphere, and begins it by applying earth more or
less mixed with chopped hay against the walls which are to support
the edifice. At the summit of the construction a hole is left for
entry and exit. During the whole of its sojourn in our country the
swallow uses this dwelling, and even returns to it for many years in
succession, as long as its work will support the attacks of time. The
faithful return of these birds to their old nest has been many times
proved by attaching ribbons to their claws; they have always returned
with the distinctive mark.
Besides the swallows, birds offer us several types of skilful
construction with tempered earth.
The flamingo, which lives in marshes, can not place its eggs on
the earth nor in the trunks of trees, which are often absent from
its domain. It builds a cone of mud, which dries and becomes very
resistant, and it prepares at the summit an excavation open to the
air; this is the nest. The female broods by sitting with her legs
hanging over the sides of the hillock on which her little family
prospers above the waters and the damp soil.
A perch in the Danube makes a dwelling of dried earth in the form of
an elliptic cupola, and prepares a semicircular opening for entry and
exit.
The bird which shows itself the most skilful mason is probably the
oven-bird (Furnarius rufus) of Brazil and La Plata. Its name is owing
to the form of the nest which it constructs for brooding, and which
has the appearance of an oven. It is very skilful and knows how to
build a dome of clay without scaffolding, which is not altogether
easy. Having chosen for the site of its labors a large horizontal
branch, it brings to it a number of little clay balls more or less
combined with vegetable débris, works them all together, and makes a
very uniform floor, which is to serve as a platform for the rest of
the work. When this is done, and while the foundation is drying, the
bird arranges on it a circular border of mortar slightly inclined
outward. This becomes hard; it raises it by a new application, this
time inclined inward. All the other layers which will be placed above
this will also be inclined toward the interior of the chamber. As
the structure rises, the circle which terminates it above becomes
more and more narrow. Soon it is quite small, and the animal, closing
it with a little ball of clay, finds itself in possession of a
well-made dome. Naturally it prepares an entrance; the form of this
is semicircular. But this is not all. In the interior it arranges
two partitions: one vertical, the other horizontal, separating off
a small chamber. The vertical partition begins at one of the edges
of the door, so that the air from without can not penetrate directly
into the dwelling, which is thus protected against extreme variations
of temperature. It is in the compartment thus formed that the female
lays her eggs and broods, after having taken care to carpet it with a
thick layer of small herbs.
The muskrats of Canada live in colonies on the banks of streams or
deep lakes, and construct dwellings which are very well arranged. In
their methods we find combined the woven shelter with the house of
built earth. Their cabins are established over the highest level of
the water and look like little domes. In building them the animals
begin by placing reeds in the earth; these they interlace and weave
so as to form a sort of vertical mat. They plaster it externally with
a layer of mud, which is mixed by means of the paws and smoothed by
the tail. At the upper part of the hut the reeds are not pressed
together or covered with earth, so that the air may be renewed in
the interior. A dwelling of this kind, intended to house six or
eight individuals who have combined to build it, may measure up to
sixty-five centimetres in diameter. There is no door directly opening
on to the ground. A subterranean gallery starts from the floor and
opens out beneath the water. It presents secondary branches, some
horizontal, through which the animal goes in search of roots for
food, while others descend vertically to pits specially reserved for
the disposal of ordure.
[Illustration: Fairy Flies (magnified 30 diameters)
1, Caraphractus Cinctus, Male; 2, 3, same, Female; 4, 5, Mymar
Pulchellus, Male and Female; 6, 7, Prestwichia Aquatica, Female and
Male; 8, Cosmocomo Fumipennis, Female]
But it is, above all, the beaver (Castor fibre) who exhibits the
highest qualities as an engineer and mason. This industrious and
sagacious rodent is well adapted to inconvenience the partisans of
instinct as an entity, apart from intelligence, which renders animals
similar to machines and impels them to effect associated acts,
without themselves being able to understand them, and with a fatality
and determination from which they can under no circumstance escape.
The civilization of the beaver has perished in the presence of man’s
civilization, or rather of his persecution. In regions where it is
tracked and disturbed by man the beaver lives in couples, and is
content to hollow out a burrow like the otter’s, instead of showing
its consummate art. It merely vegetates, fleeing from enemies who
are too strong for it, and depriving itself of a dangerous comfort.
But when the security of solitude permits these animals to unite in
societies, and to possess, without too much fear, a pond or a stream,
they then exhibit all their industry.
They build very well arranged dwellings, although at first sight they
look like mere piles of twigs, branches, and logs heaped in disorder
on a small dome of mud. At the edge of a pond each raises his own
lodge, and there is no work by the colony in common. If, however,
there is a question of inhabiting the bank of a shallow stream,
certain preliminary works become necessary. The rodents establish a
dam, so that they may possess a large sheet of water which may be of
fair depth, and above all constant, not at the mercy of the rise and
fall of the stream. A sudden and excessive flood is the one danger
likely to prove fatal to these dikes; but even our own constructions
are threatened under such circumstances.
When the beavers, tempted by abundance of willows and poplars, of
which they eat the bark and utilize the wood in construction, have
chosen a site, and have decided to establish a village on the edge of
the water, there are several labors to be successively accomplished.
Their first desire is to be in possession of a large number of felled
trunks of trees. To obtain them they scatter themselves in the
forest bordering the stream and attack saplings of from twenty to
thirty centimetres in diameter. They are equipped for this purpose.
With their powerful incisors, worked by strong jaws, they can soon
gnaw through a tree of this size. But they are capable of attacking
trees even more than 100 cm. in diameter and some forty metres in
height with great skill and adaptability; “no better work could be
accomplished by a most highly finished steel cutting tool, wielded
by a muscular human arm” (Martin). They operate seated on their
hindquarters, and they make their incision in the wood with a feather
edge. It was once supposed that they always take care so to direct
their wood-cutting task that the tree may fall on the water-side, but
this is by no means the case, and appears to be simply due, as Martin
points out, to the fact that trees by the water-side usually slope
toward the water. The austerity of labor alternates, it may be added,
with the pleasures of the table. From time to time the beavers
remove the bark of the fallen trees and feed on it.
Mr. Lewis H. Morgan studied the American beaver with great care
and thoroughness, more especially on the southwest shore of Lake
Superior; he devotes fifty pages to the dams, and it is worth while
to quote his preliminary remarks regarding them: “The dam is the
principal structure of the beaver. It is also the most important
of his erections, as it is the most extensive, and because its
production and preservation could only be accomplished by patient
and long-continued labor. In point of time, also, it precedes the
lodge, since the floor of the latter and the entrances to its chamber
are constructed with reference to the level of the water in the
pond. The object of the dam is the formation of an artificial pond,
the principal use of which is the refuge it affords to them when
assailed, and the water-connection it gives to their lodges and to
their burrows in the banks. Hence, as the level of the pond must, in
all cases, rise from one to two feet above these entrances for the
protection of the animal from pursuit and capture, the surface-level
of the pond must, to a greater or less extent, be subject to their
immediate control. As the dam is not an absolute necessity to the
beaver for the maintenance of his life, his normal habitation
being rather natural ponds and rivers, and burrows in their banks,
it is in itself considered a remarkable fact that he should have
voluntarily transferred himself, by means of dams and ponds of his
own construction, from a natural to an artificial mode of life.
“Some of these dams are so extensive as to forbid the supposition
that they were the exclusive work of a single pair or of a single
family of beavers; but it does not follow, as has very generally been
supposed, that several families, or a colony, unite for the joint
construction of a dam. After careful examination of some hundreds
of these structures, and of the lodges and burrows attached to many
of them, I am altogether satisfied that the larger dams were not
the joint product of the labor of large numbers of beavers working
together, and brought thus to immediate completion; but, on the
contrary, that they arose from small beginnings, and were built upon
year after year, until they finally reached that size which exhausted
the capabilities of the location; after which they were maintained
for centuries, at the ascertained standard, by constant repairs. So
far as my observations have enabled me to form an opinion, I think
they were usually, if not invariably, commenced by a single pair, or
a single family of beavers; and that when, in the course of time, by
the gradual increase of the dam, the pond had become sufficiently
enlarged to accommodate more families than one, other families took
up their residence upon it, and afterward contributed by their labor
to its maintenance. There is no satisfactory evidence that the
American beavers either live or work in colonies; and if some such
cases have been observed, it will either be found to be an exception
to the general rule, or in consequence of the sudden destruction of a
work upon the maintenance of which a number of families were at the
time depending.
“The great age of the larger dams is shown by their size, by the
large amount of solid materials they contain, and by the destruction
of the primitive forest within the area of the ponds; and also by
the extent of the beaver-meadows along the margins of the streams
where dams are maintained, and by the hummocks formed upon them by
and through the annual growth and decay of vegetation in separate
hills. These meadows were undoubtedly covered with trees adapted to a
wet soil when the dams were constructed. It must have required long
periods of time to destroy every vestige of the ancient forest by
the increased saturation of the earth, accompanied with occasional
overflows from the streams. The evidence from these and other sources
tends to show that these dams have existed in the same places for
hundreds and thousands of years, and that they have been maintained
by a system of continuous repairs.
“At the place selected for the construction of a dam, the ground
is usually firm and often stony, and when across the channel of a
flowing stream, a hard rather than a soft bottom is preferred. Such
places are necessarily unfavorable for the insertion of stakes in the
ground, if such were, in fact, their practice in building dams. The
theory upon which beaver-dams are constructed is perfectly simple,
and involves no such necessity. Soft earth, intermixed with vegetable
fibre, is used to form an embankment, with sticks, brush, and poles
imbedded within these materials to bind them together, and to impart
to them the requisite solidity to resist the effects both of pressure
and of saturation. Small sticks and brush are used, in the first
instance, with mud and earth and stones for down-weight. Consequently
these dams are extremely rude at their commencement, and they do not
attain their remarkably artistic appearance until after they have
been raised to a considerable height, and have been maintained, by a
system of annual repairs, for a number of years.”[12]
There are two different kinds of beaver-dams, although they are both
constructed on the same principle. One, the stick-dam, consists of
interlaced stick and pole work below, with an embankment of earth
raised with the same material upon the upper or water face. This is
usually found in brooks or large streams with ill-defined banks. The
other, the solid-bank dam, is not so common nor so interesting, and
is usually found on those parts of the same stream where the banks
are well defined, the channel deep, and the current uniform. In this
kind the earth and mud entirely buries the sticks and poles, giving
the whole a solid appearance. In the first kind the surplus water
percolates through the dam along its entire length, while in the
second it is discharged through a single opening in the crest formed
for that purpose.
The materials being prepared in the manner I have previously
described, the animals make ready to establish their dike. They
intermix their materials--driftwood, green willows, birch, poplars,
etc.--in the bed of the river, with mud and stones, so making a solid
bank, capable of resisting a great force of water; sometimes the
trees will shoot up forming a hedge. The dam has a thickness of from
three to four metres at the base, and about sixty centimetres at
the upper part. The wall facing up-stream is sloping, that directed
down-stream is vertical; this is the best arrangement for supporting
the pressure of the mass of water which is thus expended on an
inclined surface. In certain cases beavers carry hydraulic science
still further. If the course of the water is not very rapid, they
generally make an almost straight dike, perpendicular to the two
banks, as this is then sufficient; but if the current is strong, they
curve it so that the convexity is turned up-stream. In this way it is
much better fitted to resist. Thus they do not always act in the same
way, but arrange their actions so as to adapt them to the conditions
of the environment.
The embankment being completed, the animals construct their lodges.
Fragments of wood, deprived of the bark, are arranged and united by
clay or mud which the beavers take from the river-side, transport,
mix, and work with their forepaws. During a single night they can
collect as much mud at their houses as amounts to some thousands of
their small handfuls. They thus plaster their houses with mud every
autumn; in the winter this freezes as hard as a stone and protects
them from enemies. These cabins form domes from three to four metres
in diameter at the base, and from two to two and a half metres in
height. The floor is on a level with the surface of the artificial
pond. A passage sinks in the earth and opens about one and a half
metres below the level of the water, so that it can not be closed up
by ice during the severe winters of these regions.
Within, near the entry, the beavers form, with the aid of a
partition, a special compartment to serve as a storehouse, and they
there pile up enormous heaps of nenuphar roots as provisions for
the days when ice and snow will prevent them from barking the young
trunks.
A dwelling of this kind may last for three or four years, and the
animal here tranquilly enjoys the fruits of its industry as long
as man fails to discover the retreat; for the beaver can escape by
swimming from all carnivorous animals excepting, perhaps, the otter.
During the floods the level of the water nearly reaches the hut; if
the inundation is prolonged and the animal runs the risk of being
asphyxiated beneath his dome, it breaks through the upper part with
its teeth and escapes. When the water returns to its bed the beaver
comes back, makes the necessary repairs, and resumes the usual
peaceful course of its life.
We have thus seen, from a shapeless hole to these complex dwellings,
every possible stage; we have found among animals the rudiments of
the different human habitations, certain animals, indeed, having
arrived at a degree of civilization which man himself in some
countries has not yet surpassed, or even indeed yet attained.
MAN’S FIRST APPEARANCE
--BOYD DAWKINS
The characteristics of the evolution of living forms may be summed up
as follows:
I. Eocene--in which the placental mammals now on earth were
represented by allied forms belonging to existing orders and
families. Living orders and families appear; lemurs (Lemuridæ) in
Europe and North America. Evidence found in fresh-water and marine
strata; lignites.
II. Miocene--in which the alliance between living and placental
mammals is more close than before. Living genera appear; apes
(Simiadæ) in Europe and North America. Evidence--fresh-water and
marine strata; volcanic débris (Auvergne); lignites.
III. Pliocene--in which living species of placental mammals appear.
Living species appear; apes (Simiadæ) in Southern Europe. Evidence
found in fresh-water and marine strata; volcanic débris (Auvergne).
IV. Pleistocene--in which living species of placental mammals
are more abundant than the extinct. Man appears; Anthropidæ; the
palæolithic hunter; living species abundant. Evidence--refuse-heaps,
contents of caves, river deposits, submarine forests, bowlder clay,
moraines, marine sands, and shingle.
V. Prehistoric--in which domestic animals and cultured fruits appear.
Man abundant, domestic animals, cultivated fruits, spinning, weaving,
pottery-making, mining, commerce; the neolithic, bronze, and iron
stages of culture. Evidence--camps, habitations, tombs, refuse-heaps,
surface accumulation, caves, alluvia, peat bogs, submarine forests,
raised beaches.
VI. Historic--in which the events are recorded in history.
Evidence--documents, refuse-heaps, caves, tombs.
The orders, families, genera, and species in the above summary, when
traced forward in time, fall into the shape of a genealogical tree,
with its trunk hidden in the secondary period, and its branchlets
(the living species) passing upward from the Pliocene, a tree of life
with living Mammalia for its fruits and foliage. Were the extinct
species taken into account, it would be seen that they fill up the
intervals separating one living form from another, and that they too
grow more and more like the living forms as they approach nearer to
the present day. It must be remembered that in the above definitions
the fossil marsupials are purposely ignored, because they began their
specialization in the secondary period, and had arrived in the Eocene
at the stage which is marked by the presence of living genus--the
opossum (Didelphys).
It will be seen that our inquiry into the antiquity of man is limited
to the last four of the divisions. The most specialized of all
animals can not be looked for until the higher Mammalia by which he
is surrounded were alive. We can not imagine him in the Eocene age,
at a time when animal life was not sufficiently differentiated to
present us with any living genera of placental mammals. Nor is there
any probability of his having appeared on the earth in the Miocene,
because of the absence of higher placental mammals belonging to
living species. It is most unlikely that man should have belonged to
a fauna in which no other living species of mammal was present. He
belongs to a more advanced stage of evolution than the mid-Miocene
of Thenay. Up to this time the evolution of the animal kingdom had
advanced no further than the Simiadæ in the direction of man; and
the apes then haunting the forests of Italy, France, and Germany
represent the highest type of those on earth.
We may also look at the question from another point of view. If man
were upon the earth in the Miocene age, it is incredible that he
should not have become something else in the long lapse of ages, and
during the changes in the condition of life, by which all the Miocene
land Mammalia have been so profoundly affected that they have been
either exterminated or have assumed new forms. Nor in the succeeding
Pliocene age can we expect to find man upon the earth, because of
the very few living species of placental mammals then alive. It is
not until we arrive at the succeeding stage, or the Pleistocene,
when living species of Mammalia began to abound, that we meet with
indisputable traces of the presence of man on the earth. The rudely
chipped implements of the River-drift hunter lie scattered through
the late Pleistocene river deposits in southern and eastern England
in enormous abundance, and as a rule in association with the remains
of animals of Arctic and of warm habit, as well as some one or other
of the extinct species of reindeer and hippopotamus along with
mammoth and woolly rhinoceros.
The geographical change in Northern Europe at the close of the
forest-bed age was very great. The forest of the North Sea sank
beneath the waves, and Britain was depressed to a depth of no less
than 2,300 feet in the Welsh Mountains, and was reduced to an
archipelago of islands, composed of what are now the higher lands.
The area of the English Channel was also depressed, and the “silver
streak” was wider than it is now, as is proved by the raised beach at
Brighton, at Brackelsham, and elsewhere, which marks the sea-line of
the largest island of the archipelago, the Southern Island, as it may
be termed, the northern shores of which extended along a line passing
from Bristol to London. The northern shore of the Continent at this
time extended eastward from Abbeville, north of the Erzgebirge,
through Saxony and Poland, into the middle of Russia, Scandinavia
being an island from which the glaciers descended into the sea.
This geographical change was accompanied by a corresponding change
in climate. Glaciers descended from the higher mountains to the sea
level, and icebergs, melting as they passed southward, deposited
their burdens of clay and sand which occupy such a wide area in the
portions then submerged of Britain and the Continent. This depression
was followed by a re-elevation, by which the British Isles, a part of
the Continent, all the large tract of country within the 100-fathom
line, again became the feeding-grounds of the late Pleistocene
mammalia.