394 LIFE AT GREAT DEPTHS. 
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 theorizing in the right direction, 
but whose notions of the depth at which the sediments contain- 
ing invertebrata can be deposited are indefinite. These 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 care- 
ful investigations into the bathymetrical distribution of life and 
temperat The theories involving pressure and the intensity of 
the hardness of deep-sea deposits will suffer from the researches; 
but many difficulties in the way of the paleontologist will be re- 
. moved. The researches tend to explain the occurrence of a mag- 
„nificent deep-sea coral fauna in the Palæozoic times in high lat- 
itudes, and of Jurassic and Cainozoic faunas on the same area, 7: 
and they favor the doctrines of uniformity. They explain the 
cosmopolitan nature of many organisms, past and present, which 
were credited with a deep-sea habitat, and they afford the founda- 
tions for a theory upon the world-wide distribution of many forst 
during every geological formation. 
It is not advisable, however, to make too much of the intooeatial 
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 favorite 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 succeeding — 
age a new creation took place. There were as many destructions 
and creations as periods ; or, to use the words of an American geol- 
ogist, 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 astronomy. Moreover it had that 
armour of sanctity to protect it which is so hard to pierce by the 
most reasonable opposition. Nevertheless every now and then & 
Geologist recognized 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 palæ- 
* Quarterly Journal of the Geological Society of London, vol. i. p. 79. 
