CHAP. I. ] THE EQUIPMENT OF THE SHIP. 21 
the case, the sea was warm or cold at all depths, according to 
the source from which each particular layer or current of water 
was derived, and that in accordance with this arrangement we 
might have two regions separated from one another by an in- 
visible and. impalpable boundary of liquid contact, differing 
widely in climatal conditions, and showing all the consequent 
wide differences in faunze; we found that from the surface to 
the bottom the water of the sea contained organic matter in so- 
lution, or in suspension, and that therefore the Protozoa, which 
appear to pave the floor of most parts of the sea in a continu- 
ous sheet, derived by surface absorption the soft jelly of their 
bodies with the same ease and from the same source as they 
derive the carbonate of lime and the silica of their outer casings. 
These results and many others were attained or suggested by 
our first season’s very imperfect work, and they were regarded 
as so interesting and suggestive that with even greater willing- 
ness than before the Admiralty placed a gun-boat at the dis- 
posal of a committee, consisting of Dr. Carpenter, F.R.S., Mr. 
Gwyn Jeffreys, F.R.S., and myself, for the two succeeding 
summers, during which time one or more of us prosecuted the 
same line of inquiry, confirmed the result of the previous years, 
and added many new facts. The Porcupine, which we used in 
1869 and 1870, was much better suited in every way to our 
purposes than the Lightning. The weather was more favora- 
ble, and we succeeded in dredging to the depth of 2435 fath- 
oms, and establishing the fact that even at that depth the in- 
vertebrate sub-kingdoms are still fairly represented. 
Another great advance was made at this time. The register- 
ing thermometers which we used in the Lightning gave uncer- 
tain indications, and, on submitting them to experiment in a hy- 
draulic press, it was found that their error depended upon their 
bulbs being irregularly compressed by the enormous pressure 
to which they were subjected, the fluid being thus forced up 
mechanically in the tube and giving an indication higher than 
