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POPULAR SCIENCE REVIEW. 
fathoms were made by Sir J. Ross, in 1818, who, by the help of 
a machine of his own invention, brought up several pounds of 
mud from 1,050 fathoms, or above 1^ mile, in Baffins Bay, 72° 
BO 7 N., 77° 15' W. This deposit was described by Ross and 
Sabine, who accompanied him. It was a fine greenish mud, but 
no accurate determination of its nature was made. Ehrenberg, 
in 1853, examined the surface scum and mud obtained by 
Penny in 73° and 74° N., and found it to consist of — (a) Dia- 
toms (vegetable) living at the surface; ( b ) Radiolaria (animals), 
also surface-living ; and (c) sponge-spicules (animal) from the 
bottom. In 1854, Bailey determined the nature of the mud 
procured by Brooke in 900-2,700 fathoms in the Sea of Kam- 
schatka. The mud was purely silicious, there being absolutely 
no calcareous organisms. These and other observations tend 
to establish the existence of a circumpolar zone of silicious de- 
posits in the Arctic regions, within the parallel of 55° N., viz. 
a North Polar silicious cap. In 1839 an Antarctic expedition 
was despatched under Sir J. Ross, attention having been 
awakened by the appearance of Ehrenberg’s work on minute 
organisms (“Die Infusionsthierchen”), from the years 1836-38. 
This naturalist discovered that organisms whose skeletons re- 
sembled those occurring in the cretaceous and tertiary rocks, 
and sometimes constitute their whole mass, are still living. 
The observations of Dr. Hooker and of Sir J. Ross at two dis- 
tant points of the Antarctic zone proved the existence of a 
South Polar silicious cap . The discovery of an intermediate 
zone of calcareo-silicious deposit, in about 110° lat., of a 
deep sea sediment, dates back to 1853, and is due to Ehren- 
birg’s examination of soundings brought up by Berryman from 
2,000 fathoms, between Newfoundland and the Azores. These 
consisted of silicious diatoms, Radiolaria , and sponge-spicules, 
as in the Antarctic seas, but the bulk was calcareous Foraminifera. 
From this Ehrenberg concluded that “ chalk is nothing but a 
mass of dead foraminiferal skeletons.” These results have been 
confirmed by Bailey, Huxley, and others, as well as the fact of 
the extension of a similar deposit over the South Atlantic and 
into the Indian Ocean. The geological nature of the green- 
sand deposit formations was determined by Ehrenberg in 1854 ; 
and the discovery of newer greensand deposit, in 100-300 fa- 
thoms was made almost contemporaneously by Pourtales. Parker 
and Jones, too, ascertained that a formation of greensand was 
going on in the Australian seas. It is in extending some of the 
conclusions already established, and in the discovery of much 
that is wholly new to science, that the Challenger has been for 
the last three years employed.* 
* These preliminary remarks regarding the discoveries of Ehrenberg and 
others are taken from a lecture by Prof. Huxley, u On the Recent Work of 
