An Account of some Experiments on the Electricity of Tourma- 

 line, and other Minerals, when exposed to Heat. By James D. 

 Forbes, Esq. F. R. SS. L. & E., Professor of Natural Philo- 

 sophy in the University of Edinburgh. 



{Read Sd January 1832 *.) 



Although the phenomena of the Pyro- Electricity of Mine- 

 rals, as it has been termed, and those of the Tourmaline in par- 

 ticular, have, after a long period of neglect, been recently studied 

 by more than one philosopher of eminence, there are a sufficient 

 number of undetermined or debatable points, even at the thres- 

 hold of the inquiry, to yield facts of novelty and interest to those 

 who will take the trouble to look for them. 



Having during the past summer been much engaged in study- 

 ing the relations of bodies to heat and electricity, I was induced, 

 by having in my possession a considerable number of long tour- 

 malines, to repeat and endeavour to verify some recently pub- 

 lished experiments with this mineral. These inquiries brought 

 out several new facts ; and, with the hope of adding something to 

 our knowledge in this curious field, I have taken this opportuni- 

 ty of communicating to the Society the results of some very re- 

 cent experiments. 



My attention was principally directed to the verification 

 and extension of the views of M. Becquerel, whose ingenious 

 papers published in the Annales de Chimie for 1828, give us al- 

 most the only information, with the exception of a short paper 



* The publication of this paper was delayed partly under the idea of prosecut- 

 ing the experiments of which it contains an account ; but the author having en- 

 gaged in some other researches, which appear to him of more immediate importance, 

 he merely prints this communication in its original form. — Apeil 1834. 



VOL. XIII. PART I. D 



