Bath Literary and Philosophical Society. 299 



at the end of small chains about one foot asunder. This instru- 

 ment towed by a small boat, will, it is thought, completely search 

 the bed and banks of any small river. 



Mr. Rotch favoured tiie Society with the sight of a beautiful 

 glass flute, made in Paris, of very superior workmanship and 

 tone. Mr. R. expatiated at some length on tlie superiority 

 which glass possesses over every other substance for the propa- 

 gation of musical vibrations, owing to its peculiar elasticity, and 

 the high polish of which it is susceptible. 



April 14. Mr. Ricardo having directed the attention of the 

 Society to the melancholy case of imputed murder by poison, 

 which occurred lately at Falmouth, and to the conflicting opi- 

 nions of the medical men examined on the occasion ; Dr. Wil- 

 kinson remarked, that in all cases where arsenic is suspected, it 

 is unsafe to dei)end on any one apparent proof of its presence j 

 and that it is only from a combination of a great many unequi- 

 vocal proofs that a sound inference can be drawn. Although 

 the ammoniated nitrate of silver applied to a solution of arsenic 

 produces a lemon-coloured precipitate, yet the shade so nearly 

 corresponds with that arising from tiie same test in combination 

 with the phosphate of soda, that the one may be easily mistaken 

 for the other. [Perhaps the only perfect and indubitable test, 

 as stated by one of tiie witnesses on the trial, Dr. Neale of 

 Exeter, is the reproduction of the arsenic by sublimation. — 

 Editor.] 



Dr. Wilkinson afterwards resumed the explanation of his 

 mechanical theory of electricity. Metallic bodies, he observed, 

 contain the largest quantity of electricity, and non-conductors 

 the least, the quantum being always proportionate to the capa- 

 city of the substance. Thus sponge, wood, and marble, when 

 immersed in water and then removed, produce equal effects on 

 the hygrometer. The quantity of water each retains is very 

 different^ — but it is the excess above their respective capacities 

 that influences the hygrometer. The same law the Doctor ap- 

 pHed to caloric, conceiving it to be only the excess of heat above 

 the calorific capacity of the body that affects the thermometer; 

 and that to alter that capacity some clinnge in its constituent 

 parts must take place. 



In the case of a conductor of electricity, the Doctor supposes 

 this principle to prevail so much, that a continued chain of 

 communications must exist betvveen the electrical |)articles. The 

 first spark received from the prime eon<lii(i<jr of an electrical 

 machine he considers to be the natural electi icily of the con- 

 ductor driven forward by a superinduced cpiantity ; — in the same 

 manner as in the case of water impelled through a tube, the 



portion 



