Rodolfo Amedeo Lanciani.

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case, modified by the local conditions to be presently explained, of
a great general movement of Polar water toward the Equatorial
area^ which depresses the temperature of the deepest parts of the
great Oceanic basins nearly to the freezing-point.

During the first and second cruises of the ' Porcupine,' the tem-
perature of the eastern border of the great North Atlantic basin
was examined at various depths between from 64 to 2435 fathoms,
and in widely different localities, ranging from lat. 47° to lat. 66°.
The ^oWom-temperature was ascertained at thirty stations, and
serial soundings were taken at seven stations ; making the total
number of observations eighty-four. Amongst all these the coin-
cidence of temperature at corresponding depths is extraordinarily
close; the chief differences showing themselves in the tempera-
ture of the sfwrface and of the stratum immediately beneatn it.
A decided super-heating is observable in this superficial stratum,
not extending to a depth of much more than 70 or 80 fathoms,
and more considerable at the southern than at the northern sta-
tions. Whether this ' super-heating ' is entirely due to the direct
influence of solar heat, or depends in any degree on an exten-
sion of the Gulf Stream as far as the southern part of the area
examined, is a question which can only be resolved by the determi-
nation of its relative amount at different seasons. Between 100
and 600 fathoms, the rate of decrement is very slow, averaging



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Botany and Zoology. 418

only about 8® in the whole, or three-fourths of a degree for every
100 fathoms ; and this body of water has a temperature so much
above the isotherm of the northern stations, at which the observa-
tions were made, as decidedly to indicate that it must have found
its way thither from a southern source. Between 600 and 760
fathoms, however, the rate of decrease becomes much more rapid,
the reduction being 6** '4, or above 2° per 100 fathoms; while be-
tween 750 and 1000 fathoms it amounts to 3°1, bringing down the
temperature at the latter depth to an average of 38^*6. Beneath
this there is still a slow progressive reduction with increase of
depth, the temperature falling a little more than 2° between 1000
and 2435 fathoms ; so that at the last-named depth, the ^atest at
which it was ascertained, it was 36***5. — Thus it is obvious either
that the vast body of water occupying the deeper half of the At-
lantic basin has been itself derived from a colder region, or that
its temperature has been reduced by the diffusion through it of
frigid water from a Polar source. The latter supposition best ac-
cords with the gradual depression of temperature exhibited be-
tween 600 and 1000 fathoms which corresponds with the " stratum
of intermixture " of the cold area.

The temperature-soundings recently taken by Commander
Chimmo, R. N., and Lieutenant Johnson, R. N., at various points
in the North Atlantic basin, when the requisite corrections are ap-
plied for the influence of pressure on the bulbs of the unprotected
thermometers employed by them, give results which are remarka-
bly accordant with our own ; so that it may be stated with confi-
dence that the temperature of the deeper parts of the North
Atlantic sea-bed is but a very few degrees above the freezing-
point.

Now a glance at the North Polar res^ion, as laid down either on
a globe, or any projection of which t&e Pole is the center, shows
that the Polar basin is so much shut in by the northern shores of
the European, Asiatic, and American continents, that its only com-
munication with the North Atlantic basin — besides the circuitous
passages leading into Hudson's and Baflin's Bays — is the space
which intervenes between the eastern coast of Greenland and the
northwestern portion of the Scandinavian peninsula. If, therefore,
there be any such general interchange of polar and equatorial
water as that for which we have areued, the Arctic current must
flow through the deeper portions of ^is interspace, at the north of
which lies Spitzbergen, whilst Iceland and tne Faroes lie in the
middle of its southerly expanse. Now in the channel that lies be-
tween Greenland and Iceland, the depth is such as to give a free
passage to such a frigid stream; but between Iceland and the
Faroe Islands there is no depth so great as 300 fathoms at any
part, except in a narrow channel at the southeast comer of Ice-
land ; so that an effectual barrier is thus interposed to any move-
ment of frigid water at a depth exceeding this. A similar barrier
is presented, not merely by the plateau on which the British Islands
rest, but aUo by the bed of the North sea ; the shallowness of



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414 Scientific ItUeUigenct,

idiich mast give to such a movement a not leas effbotual check
than would be aiforded by an actual coast-line uniting the Shetland
Islands and Norway. Consequently, it is obvious that a flow of
ice-cold water at a depth exceeding 300 fathoms from the surface,
down the northeastern portion of this interspace, am only find its
way southward through the deeper portion of the channel between
the Faroe and Shetla^ Islands ; which will turn it into a W. S. W.
direction between the Faroe Islands and the north of Scotland,
and finally discharge such part of it as has not been neutralized by
the opposmg stream coming up from the southwest, into the great
Nortn Atlantic basin, where it will meet the Icelandic and Green-
land currents, and unite with them in diffusing Mgid waters
through its deeper portion. In thus spreacUng itsdi^ however, the
frigid water will necessarily mingle with the mass of wanner water
with which it meets, and will thus have its own temperature raised,
whilst lowering the general temperature of that mass ; and hence
it is that we do not find the temperature of even the greatest
depths of the Atlantic basin nearly so low as that of the comparar
tively shallow channel which feeds it with Arctic water.

It may be questioned, however, whether the whole body of Arc-
tic water that finds its way through the channels just indicated,
oould alone maintain so considerable a reduction in the tempera-
ture of the enormous mass which lies below 1000 fathoms in the
Atlantic basin ; subject as this must be to continual elevation by
the surface-action of the sun on its southern portion. And as the
few reliable observations on Deep-sea Temperatures under the equa-
tor indicate that even there a temperature not much above 32^
prevails, it seems probable that part of the cooling effect is due to
the extension of a flow of frigid water from the Antarctic Pole, even
north of the Tropic of Cancer. Of such an extension there is evi-
dence in the temperature-soundings recently taken in ILM.S.
* Hydra ' between Aden and Bombay, where the cooling influ^ice
oould scarcely have been derived from any other source than d»
Antarctic area.*

The unrestricted communication which exists between the Ant-
arctic area and the great Southern Ocean-basins would involve, if
the doctrine of a general Oceanic circulation be admitted, a mudi
more considerable interchange of waters between the Antarctic
and Equatorial areas, than is possible in the Northern hemisphere.
And of such a free interchange there seems adequate evia^ice;
for it is well Imown to navigators that there is a perceptible * set '
of warm sarface-water in all the southern oceans toward the Ant-
arctic Pole ; this ^ set ' being so decided in one part of the Southem
Indian Ocean, as to be compared by Oapt. Maury to the Gulf
Stream of the North Atlantic! Conversely, it would appear from

*The lowest temperature ackiaUy observed in these soundings was 36^^^. The
temperature of 33^^ given in the previous disooursei ae escusting below 1800
fathoms, proves to have been only an eetmata formed by CSaptain ShortlaQd under
the idea that the rate of reduction observed at smaller depths would oontinne
uniform to the bottom, which the aerial soundings of the * Porcupine * prove to be
by no means the case.

t ' Physical Geography of the Sea,' g§ 14»-n60.



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Botany wnd Zoohgy. 416

the application of the necessary pressure-correction to the temperar
tares taken in Sir James Ross's Antarctic expedition, the voyage
of the ^ Venus,' Ac, at depths greater than 1000 fathoms, that the
bottom-temperature of the deepest parts of the Southern Oceanic
basin really approaches the f^zing-point, or is even below it
And if the temperature of the deeper portion of the North Pacific
Ocean should be found to exhibit a depression at all corresponding
to that of the North Atlantic, it must oe attributed entirely to the
extension of this Antarctic flow; since the depth of Behring's
Strait, as well as its breadth, is so small as to permit no body of
Arctic water to issue through that channeLf ♦ ♦ ♦ ♦

The Ihraminifera collected in the * Porcupine ' expedition pre-
sent features of no less interest, though their scale is so much
smaller. The enormous mass of Globigerina^mud (sometimes al-
most pure, sometimes mixed with sand) that everywhere covers
the deep-sea bottom in the region explored, save where its temper^
ature is reduced nearly to the freezinff-point, may be jud^ea of
from the fact that in. one instance the dredge brought up Aa{^ a
ton of it from a depth of 767 fathoms. The resemblance of this
deposit to chalk is greatly strengthened by the recognition of sev-
eral characteristiciJly Cretaceous types among the Foraminifera
scattered through the mass of GloKgerincB of which it is princi-
pally composed ; as also that of JSjanthidiay frequently preserved
m flints, r^ot many absolute novelties presented tnemselves amomg
the foraminifera that form true calcareous sheUe; the chief point
of interest being the occurrence of certain types of high organi-
zation at great depths, and their attainment or a size that is only
paralleled in much warmer latitudes, or in t^e Tertiary or yet older
formations. This is especially the case with the OristeUarian
group, which has a long geological range ; and also with the MU-
fo/tms, of which specimens of unprecedented size presented them-
selves. The most interesting noveltv was a beautiful OrintolU^
which, when complete, must have haa the diameter of a sixpence,
but which, from its extreme tenuity, always broke in the process
of collection. — Of arenaceous Foraminifera, however, which con-
struct te^ by cementing together sand-grains, instead of produc-
ing shells, the number of new types is such as to seriot»ly tax
our power of inventing appropriate generic names. Many of these
types have a remarkable resemblance to forms previously known
in the Chalk, the nature of which had not been recognized. Some
of them throw an important light on tJie structure of two gigantic
arenaceous types from the ^^^ green-sand, recently described
by the speaker and Mr. H. B. Bradv, an account of which will
appear in the forthcoming part of the ^Philosophical Transactions ;'

t This statement is not in aooordanoe with the observations hitherto made on the
temperatoieB of the ocean along the Asiatic coast of the Padflc and the distribution
of oceanic UfB ; for these indicate a north Polar current as dedded as tiiat of the
lAtiantia See the iso^rmal chart of the oceans bi Dana's Report on Orustaoea,
and m this Journal, II, vol xvi, 1863, and also his Manual of Ctooloffy. The ob-
servations on the animal life of the coast, made by W. Stimpson, in the Ringgold
Szpedition, are confirmatoty evHience on this point — J. D. D.



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416 Scientific Intelligence.

and there is one which can certainly be identified with, a form
lately discovered by Mr. BL B. Brady in a clay-bed of the Carbon-
iferous limestone.

The question now arises, whether — as there must have been
deep seas in all geological periods, and as the changes which mod-
ified the climate and depth of the sea-bottom were for the most
part very gradual — we may not carry back the continuity of the
accumulation of Globigerina-mud on some part or other of the
ocean-bed into geological epochs still more remote ; and whether
it has not had the same large share in the production of the earlier
calcareous deposits that it has undoubtedly had in that of the
later. The Foraminiferal origin of certain beds of the Carbonife-
rous limestone, for example, appears to be indicated by the pres-
ence of GlobigerincB, long since observed by Professor rhillips in
sections of them, as well as bv the fact just stated. The sub-crys-
talline character of these rocts cannot be regarded as in any way
antagonistic to such an idea of their origin, since it is perfectly
well known that all traces of the organic origin of calcareous
rocks may be completely removed by subsequent metamorphism,
— as in the Chalk of the Antrim coast.

What is the source of ntUriment for the vast mass of animal
life covering the abyssal sea-bed is a question of the greatest bi-
ological interest That animals have no power in themselves of
generating the organic compounds which serve as the materials of
their bodies— and that the production of these materials from the
carbonic acid^ water, and ammonia of the Inorganic world, under
the influence of light, is the special attribute of vegetation — ^is a
doctrine so generally accepted, that to call it in question would
be esteemed a physiological heresy. There is no difficulty in
accounting for the alimentation of the higher animal types, with
such an unlimited supply of food as is afforded by the Globigerinm
and the Sponges in the midst of which thev live, and on which
many of them are known to feed. Given the Ihrotozoay everything
else IS explicable. But the question returns, — On what do these
Protozoa live ?

The hypothesis has been advanced that the food of the abyssal
Protozoa is derived from Diatoms and other forms of mmute
plants, which, ordinarily living at or near the surface, may, by
subsiding to the depths, carry down to the animals of the sea-bed
the supplies they require. Our examination of the surface-waters,
however, has afforded no evidence of the existence of such micro-
phytic vegetation in quantity at all sufficient to supply the vast
demand ; and the most careful search in the Globigenna-mud has
failed to bring to light more than a very small number of speci-
mens of these siliceous envelopes of Diatoms, which would most
assuredly have revealed themselves in abundance, had these pro-
tophytes served as a principal component of the food of the
Protozoa that have their dwelling-place on the sea-bed. — Another
hypothesis has been suggested, that these Protozoa^ which are so
near the borders of the vegetable kingdom, may be able, like
plants, to generate organic compounds lor themselves — ^manu&o-



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Botany and Zoology. 417

truing their own food, so to speak, from inorganic materials. But
it is scarcely conceivable that they should do this without the
agency of light ; and, as it is obviously the want of that agency
Tndch excludes the possibility of vegetation in the abysses of the
ocean, the same denciency would prevent animals from carrying
on the like process.

A possible solution of this difficulty, offered by Prof Wyville
Thomson in a lecture delivered last spring, has received so remark-
able a confirmation from the researches made in the ' Porcupine '
expedition, that it may now be put forth with considerable confi-
dence. It is, he remarked, the distinctive character of the Proto-
zoa^ that '' they have no special organs of nutrition, but that they
absorb water through the whole surface of their jelly-like bodies.
Most of these animals secrete exquisitely-formed skeletons, some-
times of lime, sometimes of silica. There is no doubt that they
extract both of these substances from the sea-water, although silica
often exists there in quantity so small as to elude detection by
chemical tests. All sea-water contains a certain amount of orgamc
matter in solution. Its sources are obvious. All rivers contain a
large quantity ; every shore is surrounded by a fringe, which av-
erages about a mile in width, of olive and red sea-weeds ; in the
middle of the Atlantic there is a marine meadow, the Sargasso
Sea, extending over 3,000,000 of square miles ; the sea is frdl of
animals which are constantly dying and decaying ; and the water
of the Gulf Stream, especially, courses around coasts where the
supply of organic matter is enormous. It is, ther^ore, quite in-
telli^ble that a world of animals should live in these dark abysses :
but It is a necessary condition that they should chiefly belong to
a class capable of oeing supported by absorption through the sur-
&ce of matter in solution; developing but little heat, and incui^
linff a very small amount of waste by any manifestation of vital
activity. According to this view, it seems highly probable that
at all periods of the earth's history some form of the Protozoa —
Rhizopods, Sponges, or both— -preaominated over all other forms
of animal life in the depths of the sea ; whether spreadi^, com-
pact, and reef-like, as in the Laurentian and Pal»ozoic M>zodn;
or in the forms of myriads of separate organisms, as in the Globi-
gerinoB and Ventrtculites of the Chalf *

During each cruise of the ^ Porcupine,' samples of sea-water ob-
tained from various depths, as well as from the surface, at stations
fiir removed from land, were submitted to the permanganate test,
after the method of Prof W. A. Miller, with an addition suggested
by Dr. Angus Smith for the purpose of distinguishing the organic
matter in a state of decomposition from that which is only decom-
posable; with the result of showing the unifoim presence of an
appreciable quantity of matter of the latter kind, which, not hav-
ing passed into a state of decomposition, may be ossimikMe as

• ** The Depths of the Sea," a Lecture delivered in the theatre of the BotbI Bub-
liii Sodety, April 10, 1869.
Am. Joub. 80I.-8BOOND Smuss, Vol. XLIX, No. 147.~Mat, 1870.
96



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418 Scientific InieUtgeace,

food by animals, — ^being, in fact, protoplasm in a 8tat« of extreme
dilution. And the careM analyses of larger quantities colleeted
during the third cruise, which have been smce made by Dr. Frank-
land, have fully confirmed these results, by demonstrating the
highly azotizea character of this organic matter, which presents
itself in samples of sea-water taken up at from 500 to 750 fathoms
depth, in such a proportion that its universal difiiision through the
oceanic waters may oe safely predicated.

Until, therefore, any other more probable hypothesis shall have
been proposed, the sustenance of animal life on the ocean-bottom
at any depth may be fairly accounted for on the supposition of
Prof WyVille Thomson, that the Protozoic portion of that fauna is
nourished by the direct absorption from the dilute protoplasm dif-
fused through the whole mass of oceanic waters, just as it draws
from the same mass the mineral ingredients of the skeletons it
forms. This diffused protoplasm, however, must be continually
undergoing decomposition, and must be as continually renewed;
and the source of that renewal must lie on the 9urf(ice4ife of plants
and animals, by which (as pointed out by Prof Wyville Thomson)
fresh supplies of organic matter must be continually imparted to
the oceanic waters, being carried down even to their greatest
depths by that liquid dlffuHon which was so admirably investi-
gated by the late ^ofessor Graham.

Not only, however, has the nutrition of the abyssal fauna to be
explained; its respiration also has to be accounted for; and on
this process also the results of the analyses of the gases of the
sea-water made durine the * Porcupine' expedition throw very im-
portant light. Samples were collected not only at the surface,
under a great variety of circumstances, but also frx>m great
depths ; and the gases expelled by boi ling were subjected to anid-
ysis according to the metnod of rrot Wl A. Miller — ^the adapta-
tion of his apparatus to the exigencies of ship-board having been
successfully accomplished during the first cruise by Mr. W. L. Car-
penter. The general average of thirty analyses of surface-water
gives the following as the percentage proportions: — ^25*1 oxygen,
54*2 nitrogen, 20*7 carbonic acid. This proportion, however, was
subiect to great variations, as will presently oe shown. As a gen-
eral rule, the proportion of oxygen was found to diminish, and
that of carbonic acid to increase, with the depth : the results of
analyses of intermediate waters giving a percentage of 22*0 oxy-
gen, 52*6 nitrogen, and 26*2 carbonic acid; while the results of
analyses of 6o^>m-waters gave 19*5 oxygen, 52*6 nitrogen, and
27*9 carbonic acid. But ^o^^om^water at a comparatively small
depth often contained as much carbonic acid and as little oxygen
as intermediate water at much greater depths; and the proportion
{^ carbonic add to oxygen in ^o^lom^water was found to bear a
much closer relation to the abundance of animal life (especially of
the more elevated types), as shown by the dredge, than to its
depth. This was very strikingly shown in an instance in whicb
analyses were made of the gases contained in samples of water



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Botany and Zoology. 419

collected at every 50 fathoms, from 400 fathoms to the bottom at
862 fiathoms, the percentage results being as follows :

IBOfftth. SOOfftth. Bottom. 86 ftith.
Oxygen - - 18-8 178 172

Nitrogen - - • 49*3 48-5 84.6

Carbonic add - 31-9 33*7 48*3

The extraordmarily augmented percentage of carbonic acid in
the stratum of water here immediately overlying the sea^bed was
accompanied by a great abundance of animal li& On the oth^
hand, the lowest percentage of carbonic acid found in bottom-water
— y\z: 7*9 — was accompanied by a "very bad haul" In several
cases in which the depths were nearly the same, the analyst vent-
ured a prediction as to the abundance, or otherwise, of ammal life,
from the proportion of carbonic acid in the bottom-water ; and his
prediction proved in every instance correct.

It would appear, therefore, that the increase in the proportion
of carbonic acid, and the diminution in that of the oxygen, in the
abyssal waters of the ocean, is due to the respiratory process, which
is no less a necessary condition of the existence of animal life on
the sea-bed, than is the presence of food-material for its sustenance.
And it is fiirther obvious that the continued consumption of oxy-
gen and liberation of carbonic acid would soon render the stratum
of water immediately above the bottom completely irrespirable —
in the absence of any antagonistic process of vegetation — ^were it
not for the upward diffusion of the carbonic acid through tiie in-
termediate waters to the tfwrfaoe^ and the downwa/rd diffusion of
oxygen yVom the surface to tiie depths below. A continual inters
change will take place ait the surfiace between the gases of the sea-
water and those of the atmosphere ; and thus the res|)iration of
the abyssal fauna is provided for by a process of diffusion, which
may have to operate through three milee or more of intervening
water.

The varying proportions of carbonic acid and oxygen in the atir>
/ac6-waters are doubtless to be accounted for in part hj the difibr-
ences in the amount and character of the animal life existing
beneath ; but a comparison of the results of the analyses made
during the agitation of the sur&ce by wind, with those made in
calm weather, showed so decided a reduction in the proportion of
carbonic acid, with an increase in that of oxygen, under the former
condition, as almost unequivocally to indicate that superficial dis-
turbance of the sea by atmospheric movement is absomtely neces-
sary for its purification fit)m the noxious effects of animal decom-
position. Of this view a most unexpected and remarkable con-
firmation has been afforded by the following circumstance : — In
one of the analyses of surface-water made during the second cruisey
the percentage of carbonic acid fell as low as 8*3, while that of
oxygen rose as high as 37*1 ; and in a like analysis made during
the third cmise, the percentage of carbonic acid was 6*6 ; while
that of oxygen was 45*3. As the results of every other analysis
of surface-water were in marked contrast to these, it became a
question whether they should not be thrown out as erroneous;



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420 Scientyic Intelligence,

until it was recollected that, while the samples of surface water



Online LibraryRodolfo Amedeo LancianiThe American journal of science and arts → online text (page 48 of 109)