26 



REPORT — 1866. 



The moderate depths of water that can be attained on the coast of this country 

 do not admit of any trial of the instrument as an-anged for deep soundings. 



However, some larger instruments were made, in order to test practically the 

 principle on which the pressure-gauge has been constructed, at moderate depths ; 

 and the proportions of the cylinder and of the tube (I) were so arranged that one 

 degree on the scale of the tube should be equal to j;;^ part of the volume of 

 the cylinder, and also should be one-eighth of an inch in length, so that variations 

 were read without difficulty, 



riG .1 



FI C . 3. 



F| C,4, 



In July last Thomas Sopwith, Esq., F.E.S., Captain J. E. Davis, of the Hydro- 

 graphic Department at the Admiralty, Mr. Johnson, my son and I, went to Ventnor 

 in the Isle of Wight, oiF which place is a depth of water of 40 fathoms, which is a 

 greater depth than can be conveniently obtained at any other place near the coast, 

 and we succeeded in obtaining the following series of experiments on Julv the 23rd, 

 24th, 25th, 26th, and 31st :— 



8 were made at the depth of 10 fathoms. 

 13 



7 



7 



8 

 22 



12 



The results of experiments are shown in the annexed diagram. On every occasion 

 the compression at the greatest depth was recorded, and appeared to be nearly in 

 proportion to the depth. The ratio of compression for sea- water, which has a den- 

 sity of 1.027'equal to the density acquired by fresh water, according to INIr. Perkins's 

 experiments, under a pressure of about 600 atmospheres, appears to be ^^ part 

 for a depth of 10 fathoms— in the moderate available depth for experiments. 



These experiments are considered to have established the principle of the instru- 

 ment as sound. Still, a series of experiments at gi-eater depth appears necessary to 

 test the instruments under various conditions of depth, temperature, &c., and also 

 to construct a table of depths to be used in deep-sea soundings, and which can be 

 arranged in fathoms. 



The deep-sea thermometer is intended to be used at the same time with the deep- 



