OBSERVATIONS ON ERUPTIONS OF LUNAR VOLCANOS. C 20\ 



in thofe who govern it, might enrich the fcience with new 

 difcoveries. An acquaintance with the effects of the re- 

 fraction of the air might be difleminated by daily experiments ; 

 meteorology, which is the leaft cultivated, and perhaps the 

 moft difficult branch of natural philofophy, might be ftored 

 with difcoveries on the influence of heat and cold, humidity, 

 ftorms, changes of weather, fogs, fnow and rain, as well as 

 that produced by feveral other meteors on the tranfparency 

 of the air ; a daily comparifon of the indications given by 

 the barometer, the hygrometer, the anemometer, and the 

 electrometer, with thofe of the diaphanometer of M. de Sauf- 

 fure *, and of the cyanometer t, might, in time, lead to very 

 unexpected refults. 



At the conclufion of the work, the chevalier notices the Englifli tele- 

 telegraph erected on our admiralty, which appears to have S ra P h « 

 been an invention fubfequent to his, and to be Jefs complete. 

 His telegraphs were eftablifhed in Sweden in 1794, ours was 

 not erected until 1796, and the number of its fignals does 

 not exceed 64, unlefs thofe are reckoned which depend on 

 the order in which the mutters are fliown, and which ar« 

 liable to great ambiguity. 



IX. 



Additional Obferrations on the Probability that the Eruptions of 

 Lunar Volcanos may fomttimes reach the Earth, By a Cor- 

 refpondeut. 



To Mr. NICHOLSON. 

 SIR, 



uOME time ago, I addrefled a letter to you, on the pro- 

 bability that the eruptions of lunar volcanos may fometimes reach 

 the earth ; which was inferted in your Journal for December 

 laft. I will now beg leave to trouble you with a few additional 

 obfervations on the hypothefis, I there ventured to advance. 



* EJfayfur VHygrometrie, §371. 



+ S£e a defcription of this inftrument in obfervations fur la 

 jphifique et fur l'Hiftorie Naturelle, par Roller, 1791, mars, p. 199. 



In 



