614 
NATURE 
[| April 14, 1870 
early days of geology, when the destructive influence of chemical 
processes in strata upon the remains of organisms in them was 
hardly admitted. 
The great value of such researches as those so ably carried out 
by Thomson, Carpenter, and Jeffreys, is the definite knowledge 
they impart to the geologist who is theorising in the right direc- 
tion, but whose notions of the depths at which the sediments 
containing Invertebrata can be deposited, are indefinite. The 
researches contribute to more exact knowledge, and they will 
materially assist the development of those hypotheses which are 
current amongst advanced geologists into fixed theories. I do 
not think that any geological theory worthy of the term, and 
which has originated from geological induction, will be upset by 
these careful investigations into the bathymetrical distribution of 
life and temperature. Physicists have propounded theories 
which have been accepted by some geologists; but they are 
looked upon as doubtful hypotheses by others. Paleeontologists 
and such theories have constantly been at issue. The theories 
involving pressure and the intensity of the hardness of deep- 
sea deposits will suffer from the researches; but many, diffi- 
culties in the way of the paleontologist will be removed. 
The researches explain the occurrence of a magnificent deep- 
coral fauna in the Paleozoic times in high latitudes, and 
of Jurassic and Cainozoic faunas on the same area, and they 
tend more than ever to the doctrines of uniformity. They ex- 
plain the cosmopolitan nature of many organisms, past and 
present, which were credited with a deep-sea habitat, and they 
afford the foundations for a theory upon the world-wide distribu- 
tion of many forms during every geological formation, It is not 
advisable, however, to make too much of the interesting identities 
and resemblances of some of the deep-sea and abyssal forms with 
those of such periods as the Cretaceous, for instance. In the 
early days of geological science there was a favourite theory that 
at the expiration of a period the whole of the life of the globe 
was destroyed, and that at the commencement of the succeed- 
ing, anew creation took piace. There were as many destruc- 
tions and creations as periods, or, to use the words of an 
American geologist, there was a succession of platforms. This 
theory held back the science, just as the theory that the sun 
revolved round the earth retarded the progress of astro- 
nomy. Moreover, it had that armour of sanctity to protect 
it which is so hard to pierce by the most reasonable opposi- 
tion. Nevertheless every now and then a geologist recognised 
the same fossils in rocks which belonged to different periods. 
A magnificent essay by Edward Forbes on the Cretaceous Fossils 
of Southern India, a wonderful production and far before its 
age,* gave hope and confidence to the few paleeontologists who 
began to assert that periods were perfectly artificial notions ; 
that it did not follow because one set of deposits was forming in 
one part of the world, others exactly corresponding to it else- 
where, so far as the organic remains are concerned, were con- 
temporaneous; and that life had progressed on the globe 
continuously and without a break from the dawn of it to the 
present time. The persistence of some species through great 
vertical ranges of strata, and the relation between the world-wide 
distribution of forms and this persistence, were noticed by 
d’Archiac, de Verneuil, Forbes, and others. The identity of 
some species in the remote natural-history provinces of the 
existing state of things, was established in spite of the dogmatic 
opposition of authorities; and these geologists accepted the 
theories that there were several natural-history provinces during 
every artificial period; that some species lived longer and 
wandered more than others; and that some have lasted even 
from the Palaeozoic age to the present. Persistence of type was 
the title of a lecture delivered by Professor Huxley many 
years ago; and this persistence has been admitted by every 
palzontologist who has had the opportunity of examining large 
series of ‘fossils from every formation from all parts of the 
world. 
Geological ages are characterised by a number of organisms 
which are not found in others, and by the grouping of numerous 
species which are allied to those of preceding and succeeding 
times, but which are not identical. Certain portions of the 
world’s surface were tenanted by particular groups of forms 
during every geological age, and there was a similarity of 
arrangement in this grouping under the same external physical 
conditions. ‘To use Huxley’s term, the ‘‘ homotaxis”’ of certain 
natural history provinces during the successive geological ages 
* Trans. Geol. Soc. 
+ Royal Institution. See also Pres. Address, Geol. Soc. 
has been very exact. The species differed, but there was a 
philosophy in the consecutive arrangements of high-land and 
low-land faunas and floras, and of those of shallow seas, deep 
seas, oceans, and reef-areas. The oceanic* conditions, for 
instance, can be traced by organic remains from the Laurentian 
to the present time, and the deep-sea corals now under con- 
sideration are representative of those of older deep seas. The 
species which are new, and the varieties of those which have 
been already noticed, will be described and drawn in other 
communications. It is not a matter for surprise, then, that 
there being such a thing as persistence of type and of species, 
some very old forms should have lived on through the ages 
whilst their surroundings were changed over and over again. But — 
this persistence does not indicate that there have not been suffi- 
cient physical and biological changes during its lasting to alter 
the face of all things enough to give geologists the right of 
asserting the constant succession of periods. ‘The occurrence of 
early Cainozoic Madreporaria in the deep sea to the north-west 
of Great Britain only proves that certain forms of life have per- 
sisted during the vast changes in the physical geography of the 
world which were initiated by the upheaval of the Alps, the 
Himalayas, and large masses of the Andes. To say that we are 
therefore still in the Cainomsic age would hardly be consistent 
with the necessary terminology of geological science. 
During the end of the Miocene age, and the whole of the 
Pliocene, the Sicilian area was occupied by a deep sea. The 
distinction between the faunas of those times and the present 
becomes less, year after year, as science progresses; and it is 
evident that a great number of existing species of nearly every 
class flourished before the occurrence of the great changes in 
physical geology which have become the artificial breaks of 
classificatory geologists. That the Cainozoic deep-sea corals 
should resemble, and in some instances should be identical in 
species with, the forms now inhabiting vast depths, is therefore 
quite according to the philosophy of modern geology. Before 
the deposition of the Cainozoic strata, and whilst the deep-sea 
deposits of the Eocene age were collecting in the Franco-British 
area, there was a Madreporarian fauna there which was singularly 
like unto that which followed it, both as regards the shape of 
the forms and their genera. Still earlier, during the slow subsi- 
dence of the great Upper Cretaceous deep-sea area, there was a 
coral fauna in the north and west of Europe, of which the 
existing is very representative. The simple forms predominate 
in both faunas. Caryophyliia is a dominant genus in either, and 
a branching Syheléa of the old fauna is replaced in the present 
state of things by a branching Lephohelia. The similarity of 
deep-sea coral faunas might be carried still further back in the 
world’s history ; but it must be enough for my purpose to assert 
the representative character and the homotaxis of the Upper 
Cretaceous, the Tertiary, and the existing deep-sea coral faunas. 
This character is enhanced by the persistence of types; but 
still the representative faunas are separable by vast intervals 
of time. P. M. DuNcAN 
SOCIETIES AND ACADEMIES 
LONDON 
Royal Society, March 31.—‘‘ On the relation between sun’s 
altitude and the chemical intensity of total daylight in a cloudless 
sky.” By Henry E. Roscoe, F.R.S., and T. E. Thorpe, Ph.D. 
In this communication the authors give the results of a series of 
determinations of the chemical intensity of total daylight made 
in the autumn of 1867 on the flat tableland on the southern side 
of the Tagus, about 84 miles to the south-east of Lisbon, under 
a cloudless sky, with the object of ascertaining the relation 
existing between the solar altitude and the chemical intensity. 
The method of measurement adopted was that described in a 
previous communication to the Society,+ founded upon the 
exact estimation of the tint which standard sensitive paper 
assumes when exposed for a given time to the action of daylight. 
The experiments were made as follows :—1. The chemical action 
of total daylight was observed in the ordinary manner. 2. The 
chemical action of the diffused daylight was then observed by 
throwing on to the exposed paper the shadow of a small blackened 
brass ball, placed at-such a distance that its apparent diameter, 
seen from the position of the paper, was slightly larger than that 
of the sun’s disk. 3. Observation No. I was repeated. 4, Ob- 
servation No. 2 was repeated. ’ 
* P. M. Duncan, Quart. Journ. Geol. Soc. No. 1or- 
+ Roscoe, Bakerian Lecture, 1865. 
