186 On a ncxo Method of taking Deep Soundings in tlie Ocean. 



that the «Tlobe had been unable to support a pressure eighty 

 times that of the atmosphere, unbalanced by any resistance 

 within ; it had burst as if by an explosion. Another machine 

 composed entirely of wood also disappeared ; and it has been 

 found that most of the solid substances of low specific gravity, 

 such as every species of wood and even cork, however lightly 

 they may float on the surface, will have the water forced into 

 their pores, as well as the mass itself compressed, when ex- 

 posed to such enormous pressure of the fluid, from which they 

 return no longer capable of floating. 



The only resource will therefore be to use some fluid equally 

 incompressible with water, and of less specific gravity; among 

 these oil is the most eligible, as the liquids possess no affinity 

 for each other, and may be allowed to come in contact without 

 any danger of admixture. This should be substituted for the 

 air in the copper receiver, and an aperture made in the lower 

 part to admit the water should a vacuum occur in the inside, 

 but too small to allow the oil to escape if the apparatus be 

 accidentally reverted. In case of any compression of the oil, 

 the water will merely rise in the interior without any danger 

 of fracturing the receiver, whose strength, and consequently 

 weio-ht, may be reduced merely to that necessary to the pre- 

 servation of its form. The globular form is the best, as it has 

 the greatest capacity with the least surface. The oils vary in 

 their specific gravity from -85 to more than r. If we take 9' 

 as an average attainable degree of lightness, a buoy of one 

 cubic foot capacity, or a sphere of one and a half foot in dia- 

 meter, will have a floating power of six pounds, which it will 

 retain in every depth unless the compression of the oil pro- 

 ceeds at a much greater ratio than that of sea-water, which 

 doubles its mass, under its own weight, at a depth of ninety 

 miles ; but this can only be ascertained by experirtient. La- 

 place estimated the mean depth of the Pacific Ocean at four, 

 and that of the Atlantic at three, miles ; this was deduced from 

 his calculations relative to the tides, and he supposed that there 

 was no very extensive variation from this average. At such a 

 depth the quantity of air contained in a buoy of one foot ca- 

 pacity would be compressed into two inches and a half, and a 

 hollow globe, such as Mr. Massey used, would sustain a pres- 

 sure of more than four tons on each inch of surface. 



It may not be impossible to fix a detonating ball so that it 

 shall explode on emerging into the air, and thus announce the 

 return, and indicate the position, of the instrument, which will 

 be exposed to various currents at diffei-ent depths, and may be 

 floated to a distance, and in a direction, entirely unexpected. 

 It will be a long process to lay down the soundings of the 



