Effect of Pressure on Electric Conductibiliiy in Wires. 441 



The effect of season was to cause a diminution of all the respira- 

 tory phenomena as the hot season advanced. The maximum state 

 was in spring, and the minimum at the end of summer, with periods 

 of decrease in June and of increase in Octoher. The diminution in 

 the author was 30 per cent, in the quantity of air, 32 per cent, in the 

 rate of respiration, and 1 7 per cent, in the carhouic acid. The in- 

 fluence of temperature was considered in relation to season, and it 

 was shown that whilst sudden changes of temperature cause imme- 

 diate variation in the quantity of carbonic acid, a medium degree of 

 temperature, as of 60°, is accompanied by all the variations in the 

 quantity of carbonic acid, and that there is no relation between any 

 given temperature and quantity of carbonic acid at different seasons. 

 Whatever was the degree of temperature, the quantity of carbonic 

 acid, and all other phenomena of respiration, fell from the heginning 

 of June to the beginning of September. The author then described 

 the influence of atmospheric pressure, and stated that neither 

 temperature nor atmospheric pressure accounts for the seasonal 

 changes. 



The kinds of exertion which had been investigated were walking 

 and the treadwheel. AValking at two miles per hour induced an ex- 

 halation of 18-1 grs. of carbonic acid per minute, and at three miles 

 per hour of 25'83 grs. ; whilst the effect of the treadwheel at Cold- 

 bath Fields Prison was to increase the quantity to 48 grs. per mi- 

 nute. All these quantities vary with the season, and hence the 

 author recommends the adoption of relative quantities, the compari- 

 son being with the state of the system at rest, and apart from the 

 influence of food. 



January 27. — Sir Benjamin C. Brodie, Bart., President, in the Chair. 



The following communication was read : — 



" On the Effect of Pressure on Electric Conductibihty in Mctalhc 

 Wires." In a Letter from M. Elie Wartmann of Geneva, toMajor- 

 General Sabine, Treas. andV.P.R.S. 



Geneva, January 3rd, 1859. 



My dear Sir, — The newspapers having reported that a society of 

 English shareholders intends to lay a second cable for transatlantic 

 telegraph}^ you will allow me to give here a brief account of some 

 experiments 'by which I have succeeded in proving the effect of 

 pressure on electric conductibility in metallic wires. 



The method which I have resorted to is the one devised by 

 MM. Christie and Wheatstonc, which is called the electrical bridge. 

 The current of a Bunsen's battery of six large cells was divided 

 between the wire to be tested (a very soft copper wire 0-05 of an 

 inch in diameter, and covered with gutta percba) and another con- 

 ductor ; both being connected with a delicate lluhmkorff's galvano- 

 meter, so that the needle remained on the zero point. All contacts 

 were made invariable by solderings. 



No sensible effect being determined by the pressure of nine atmo- 



