842 
much greater than that. Indeed, we now 
know that more than one half of the actual 
surface of the globe is over two miles be- 
neath the surface of the water, and that 
about seven million square miles are buried 
under more than 3,000 fathoms of ocean. 
Still greater depths are by no means un- 
common. The Challenger sounded at a 
depth of 4,561 fathoms in the North Atlan- 
tic, and Uncle Samuel, not to be outdone by 
his British brother, very recently found a 
depth of 5,200 fathoms near the lately ac- 
quired Island of Guam. This is, so far as 
we know, the deepest abyss of the ocean, 
being 31,200 feet, or nearly six miles. Into 
such a depth the highest terrestrial moun- 
tain could be plunged without any resultant 
peril to navigation, as there would still be 
some 2,000 feet above the highest crest. 
As already indicated, this vast realm of 
darkness was unexplored previous to about 
the middle of the nineteenth century. The 
pioneer explorer of the sea bottom was a 
Norwegian zoologist, Michael Sars. Then 
followed several expeditions under the 
patronage of the British Government, cul- 
minating in the Challenger voyage, the re- 
suits of which stand to-day as a peerless 
example of a wise and liberal policy in the 
encouragement of scientific research. 
The United States has come well to the 
front in deep-sea investigation, and now 
owns the best equipped vessel for this work 
in the world. I refer to the Albatross, of 
which we shall hear more later. Ameri- 
cans may well take pride in remembering 
that the oceanic basins near our eastern and 
southern coasts are more thoroughly ex- 
plored thanany other partsof the sea bottom. 
Investigations of this nature have been 
attended with almost insuperable difficul- 
ties, necessitating the devising of a number 
of entirely novel instruments and machines 
for this particular work. Several of the 
most successful of these were invented by 
American naval officers, of whom Captain 
SCIENCE. 
[N.S. Vou. XIII. No. 335. 
Sigsbee, of the ill-fated Maine, has been 
the most prominent. Our knowledge of 
_the sea bottom has been gained mainly by 
the use of the following appliances : 
1. The sounding machine. To drop a 
weight attached to a line to the bottom of 
the sea would seem to be as simple a propo- 
sition as could well be devised. As a mat- 
ter of fact, however, its successful accom- 
plishment has taxed the inventive genius 
of the most accomplished engineers. Sigs- 
bee’s sounding machine, with detachable 
weight and piano-wire line has proved the 
best device for obtaining accurate soundings 
and adequate samples of the bottom. This 
and the other instruments about to be men- 
tioned will be illustrated and briefly ex- 
plained later. 
2. The thermometer. Temperature obser- 
vations have been of the utmost importance 
in determining the physical conditions of 
the deep sea, and various kinds of ther- 
mometers have been devised to withstand 
the enormous pressure and register the 
maximum and minimum heat. Not infre- 
quently these expensive instruments have 
been brought to the surface with their bulbs 
crushed to powder by the terrific pressure 
of the abyss. 
3. The water bottle. Not only must depth 
and temperature be ascertained, but the 
actual composition and condensation of 
the water must be found by means of sam- 
ples that can be secured free from admix- 
ture with sea water of other depths. Here 
also the genius of Captain Sigsbee was equal 
to the emergency, and the ‘Sigsbee water 
bottle’ has proved itself a convenient and 
efficient instrument, being so constructed 
that it will take a sample of water at any 
given depth and then automatically seal 
itself and remain hermetically closed until 
opened by hand. 
4, The dredge, for scraping over the bot- 
tom and securing specimens of the animal 
life of the deep. 
