NATURAL PHILOSOFHT. 171 



depths. The discovery of the Messrs. Morse was that of the 

 means of making a buoy which will retain its buoyancy under 

 the enormous pressm-e of the deep sea. They took a hollow 

 glass sphere between 3 and 4 inches in diameter, the glass only a 

 tenth of an inch thick, and the sphere so light that it floated in 

 water with half its bulk above the surface, and subjecting this 

 fragile body in the cistern of an hydraulic press to a pressure of 

 7 tons on the square inch, which is the pressure at the depth of 

 about 30,000 feet in the ocean, they found that the spher.e was 

 neither crushed nor permeated by the liquid. A tin or wooden 

 tube, 4 inches or more in diameter, and of any required length, is 

 filled with these glass spheres, and ballasted so that it will float 

 upright in the water. An elongated sinker, also, of any required 

 length and weight, is then suspended from the bottom of the 

 tube, and so attached there that it becomes detached when the 

 weight touches, or, if desired, when it is 100 feet, or any required 

 distance, from the bottom, leaving the tube with its spheres to 

 ascend to the surface. As this instrument moves with uniform 

 velocity both in its descent and ascent, the time of its disappear- 

 ence from the surface indicates the depth to which it has de- 

 scended. But the inventors do not confine themselves to this 

 mode of determining the depth. They enclose in their tube, and 

 send down and bring back with it their proper bathometer, which 

 is simjily a bottle of water with a bag of mercury and water sus- 

 pended from its neck, the water in the bottle being connected 

 with the mercury in the bag by a glass tube, of very fine bore, 

 passing from the bottom of the bag through an India-rubber stop- 

 per in the neck of the bottle into its interior. When this bottle 

 and bag are placed at the bottom of the sea, the pressure of the 

 external water, communicated through the bag and through the 

 mercury in the bag and glass tube to the water in the bottle, 

 compresses that water, and mercury is forced from the bag into 

 the bottle, to supply the void caused by the compression. The 

 amount of the mercury forced into the bottle is the measure of 

 the compression of the water, and the com.pression of the water is 

 the measure of the height of the compressing column, that is, 

 of the depth of the sea. To facilitate the measuring of the mer- 

 cury, there is inserted in the bottle, opposite the neck, a gradu- 

 ated tube of evenbcn'c, closed at its outer end, so that on inverting 

 the bottle the mercury falls into this metre-tube, and the height 

 of the mercury indicates the depth to which the bottle has de- 

 scended. 



All attempts to measure the deep sea with a line and sinker 

 attached, as in ordinary soundings, have proved failure-s, and sci- 

 entitic men of the highest reputation, who have devoted much 

 time to the investigation of the problem, have pronounced it im- 

 possible ever to send and recover a line with a sinker from the 

 greatest depths of the ocean. Even in moderate depths the 

 measurement l)y a line is very uncertain and unreliable, in con- 

 sequence of the effect of currents, and of the drifting of the boat 

 from which the soundings are made. The bathometer of the 

 Messrs. Morse, it is asserted, Avill descend to, and return from. 



