38 
CRUISE OF H.M.S. CHALLENGER. 
entirely devoid of animal life. This newly dis- 
covered formation going on at the bottom of the 
sea appeared, as was found afterwards, to extend for 
some 350 miles, when the depth decreased gradually 
until 2000 fathoms was obtained, and the dredge 
brought up animal life. The nature of the bottom 
changed gradually into the usual Atlantic ooze, 
altering again in a few days, as the depth increased 
to 3000 fathoms, when the mud lost all trace of 
carbonate of lime and resumed its red colour, which 
continued to within 100 miles of Sombrero. The 
analysis of this red deposit proved it to be almost a 
pure clay (a silicate of alumina and the oxide of 
iron, with a small portion of manganese). From 
these results it was inferred that the circumstances 
which lead to the deposition of this bottom were 
the cause of its being so unfavourable to the develop- 
ment of species; and, although it has been since 
proved that animal life is possible at all depths, it has 
been found, after reaching, say, 1000 iathoms, that its 
abundance greatly diminishes. It was in one of these 
dredgings we were successful in obtaining a beau- 
tiful blind Crustacea, perfectly transparent, which, 
although found at such great depths, does not appear 
to suffer from this peculiarity either in development 
or colour, nature having supplied claws and feelers 
to make up for the suppression of eyes, the sense of 
vision being useless in its normal state of perpetual 
darkness. 
