1823.] Electromagnetism by Heat. 429 



was 6i° ; with the same length of platina wire of l-100th inch, 

 not more than i°. 



With four feet of copper wire of l-12th inch, the deviation 

 was 21°, and was not increased by using two such wires. 



In all these experiments, the deviation was in the same 

 direction throughout every part, both of the bars and of the 

 connecting wires. 



No difference of effect was observed, whether the bars were 

 after fusion cooled slowly or rapidly. 



The effects were not materially increased by increasing the 

 dimensions of the bars, or of the surfaces ill contact. 



A tourmaline, which by heat exhibited the opposite electric 

 states very strongly, produced no deviation on the magnetic 

 needle, when its ends were connected with the galvanoscope by 

 silver wires coiled round them. 



For a comparison between the electromagnetic effects as 

 produced by heat and by the usual process, it was observed that 

 rods of zinc and copper, each 7-10ths of an inch in diameter, and 

 distant 4-10ths, when excited by equal parts of muriatic acid 

 and water, produced a deviation of 27° on the large compass ; 

 and rods of 3-10ths distant 3-1 Oths inch, gave 40° with the 

 smaller. Believe me, dear Sir, 



Very sincerely yours, 



J.CUMMING. 



Article VI. 





Experiments to determine the Practicability of an Operation for 

 Phthisis Pulmonalis, proposed by Dr. Carson. By David 

 Williams, MD. 



(To the Editor of the Annals of Philosophy.) 



SIR ? Liverpool, May 4, 1823. 



The following experiments were instituted from a desire to 

 examine a very important physiological hypothesis, advanced 

 by Dr. Carson. That gentleman has published a pamphlet,* 

 consisting of three essays : one, on the Elasticity of the Lungs ; 

 another, on the Vacuity of the Arteries after Death ; and the 

 third, on Lesions of the Lungs. In the second, or that on the 

 Vacuity of the Arteries after Death, he relates two methods 

 that he adopted for killing animals, by admitting air through 

 different parts of the parietes of the chest into both its cavities 

 simultaneously, thereby collapsing the lungs. One method was 

 by making an opening of about an inch in length between a pair 

 of the ribs on each side of the thorax. The other was by making 



• E«ays, Physiglogical and Practical. Py James Carson, WD. 



