406 PHILOSOPHICAL TRANSACTIONS. [aNNO 1 773, 



rounding laminae of metal, it is necessarily acciimul;ited to a quantity which, 

 if we may judge from the touch, is more than sufficient to fire the dry cupreous 

 salt. The salt formed with tin, and the nitrous acid, burns and sparkles in a red 

 heat. Catching fire therefore, from the ignited cupreous* salt, it burns with it,; 

 and assists in the detonation, which is common to all nitrous compositions in 

 similar circumstances. 



If the salt be very wet, there will not be much fire or explosion, because the 

 heat will be dissipated before the salt can be sufficiently dried in every part. If 

 the salt be not moist, it cannot commence the action which is necessary; and 

 there will be no fire, because there can be no hasty solution of the tin to give 

 the requiste heat. If the tin and salt be not coiled up in due time, there will 

 be very little heat, and no fire; because the dissipation of the heat from a broad 

 expanse, keeps pace with the generation of it; and as the moisture exhales 

 quickly in this manner, there is none left to renew the action on the tin and 

 consequent heat, when the proper time of coiling has elapsed. 

 iJ A piece of tin foil, larger than that above described, cannot easily be managed; 

 stnaller pieces give less fire in the direct proportion of their surfaces, and the quan- 

 tity of salt which they can, at the same instant, reduce to the required state of 

 dryness. The sudden dissipation of the moisture appears the most curious of 

 these phenomena. To render it the more observable, he made the following 

 experiments: he placed a piece of tin foil, 12 inches long by 2 broad, loosely 

 coiled, and standing vertically on the flattest end, in half a table-spoonful of the 

 saturated solution of copper in the diluted nitrous acid; and found that scarcely 5 

 seconds elapsed, from the time when a brisk effervescence, accompanied with 

 weak nitrous fumes, arose, till the liquor became a consistent mass, and sparks 

 of fire issued from the coils of tin; which having attracted part of the solution 

 above the common level, brought it into the condition in which it is readily 

 dried, heated, and fired. 



A like quantity of the same solution, kept in a strong boiling heat, does not 

 acquire such consistence in a ten fold space of time. The hasty exhalation 

 therefore, is not caused by the heat alone; neither does it seem to require any 

 grc!at surface. What else it is owing to, he commits a while to the examination 

 of the curious. 



XVII. Extracts of some Letttrs, from Sir Wm. Johnson, Bart., to Arthur Lee, 

 M. D., F. R. S., on the Customs, Manners, and Languages of the Northern 

 Indiaiis of America, p. 142. 



In all inquiries of this sort, we should distinguish between the more remote 

 tribes, and those Indians, who, from their having been next to our settlements 

 tor several years, and relying solely on oral tradition for the support of their 



