18^3.] Proceedings of Philosophical Societies, Wt 



considerably increased their electricity, and at the same time 

 produced a smell similar to that which is often perceived whea 

 the cushion of an electrifying machine rubs against the cylin- 

 der." P. 598, 599. 



The Aurora did not often appear immediately after sun-set. 

 It seemed that the absence of that luminary, for some houm, 

 was in general required for the production of a state of atmo^ 

 spere, favourable to the generation of the Aurora. On one 

 occasion only (March 8th, 1821), did I observe it distinctly, 

 previous to the disappearance of day-light," P. 599. 



" I have never heard any sound that could be unequivocally 

 considered as originating in the Aurora; but the uniform tes- 

 timony of the natives, both Crees, Copper Indians, and Esqui- 

 maux, and of all the older residents in the country, induces me 

 to believe that its motions are sometimes audible. These in- 

 stances are, however, rare ; as will appear, when I state that I 

 have now had an opportunity of observing that meteor for up; 

 wards of two hundred different nights." Ibid. 6. 



Article XIII. 



Proceedings of Philosophical Societies, 



ROYAL SOCIETY. 



May 29.— At this meeting, the reading of Mr. W. S. Harris's 

 Account of a Magnetic Balance, and of some recent Experi- 

 ments on Magnetic Attraction, was resumed and concluded. 



The construction of the magnetic balance is analogous to that 

 of the electrical balance, described by Mr. Harris in his Obser* 

 vations on the Effects of Lightning on Floating Bodies, lately 

 pubhshed : the experiments made with it were on the laws wMck 

 govern the force of attraction in magnetized bodies, under dif- 

 ferent circumstances of distance, &c. 



At this meeting, also, the reading of the following paper was 

 commenced : A Case of Pneumato Thorax, with experiments 

 on the absorption of different kinds of air introduced into the 

 pleura; by John Davy, MD. FRS. 



June 5. — The reading of Dr. Davy's paper was resumed and 

 concluded. 



The case described by Dr. Davy was one of Phthisis Pulmo- 

 nalis, which proved rapidly fatal, owing to the supervention of 

 Pneumato Thorax. A few hours after death, the chest was perfo- 

 rated under water, and nearly 226 cubic inches of air were col- 

 lected from the right pleura, into which it had passed by means 

 of an ulcerated opening communicating indirectly through a 

 vomica with the bronchia. This air was found to consist of 



