198 Annals of the Philosophical Club 



Physician had not been respected, another person having 

 been appointed, without justification, to receive his salary. 

 A second letter, similarly found, written officially to Prince 

 Rupert, describes a visit to Prince Maurice, and states that 

 the army was suffering from fever. He mentions that, 

 having found some one in a very bad state, he determined 

 not to give him any medicine. 



Professor Flower exhibited a piece of the Demerara sub- 

 marine telegraph, the gutta-percha coating of which had 

 been cut through (and its action stopped) by the rostrum 

 of a sawfish, one of the teeth of which was left in the coating. 

 Dr. Giinther said the sawfish is supposed to feed on the 

 intestines of other fish, its mouth being lined with rows of 

 very minute teeth, so that it probably used its rostrum to 

 cut them open. In this case it was very likely near the 

 bottom. 



1876. Feb. 24th, 259th meeting. Dr. Siemens ex- 

 plained the principle of an apparatus, which he called a 

 bathometer and had devised for ascertaining the depth 

 of the sea without using a sounding wire. This was done 

 by measuring the effect produced by a diminution in density 

 of the attracting body. As the material of the earth is 

 more dense than sea- water, gravitation at its surface should 

 be greater than at that of the ocean. The instrument for 

 measuring the difference consisted of a vertical tube with 

 cup-like extremities, containing mercury, which pressed 

 upon an elastic steel diaphragm, supported in the centre 

 by carefully tempered steel springs. It was so arranged 

 as to compensate for variation of temperature, and being 

 open at both ends was not affected by that of atmospheric 

 pressure. The effect of latitude had been calculated in 

 iathoms of depth, and tabulated for use with the instrument. 

 Dr. Siemens said that a comparison of the instrument's read- 

 ings with those obtained from Sir W. Thomson's sounding 

 wire justified the expectation that it would indicate to the 

 mariner changes of depth long before he reached really 

 dangerous ground. 



An attraction meter had been constructed on the same 



