1826.] Telescopical Observations on the Moon. 337 



not, some critic might accuse me of thinking charcoal necessary 

 for the process/^ My criticism takes another direction than that 

 which you apprehended ; for I assert, although you are unac- 

 quainted with the fact, that charcoal is as necessary in reducing 

 the sulphuret of arsenic as the oxide ; and the experiment upon 

 which this conclusion is founded is this : — I mixed one part of 

 orpiment with about two parts of carbonate of soda ; the mixture 

 was subjected to a red heat until all fumes ceased. On examin- 

 ing the residual mass, I found it to consist of carbonate, sul- 

 phate, and arseniate of soda, and consequently the whole of the 

 arsenic cannot be procured by means of an alkah without the 

 assistance of charcoal, whether we act upon the oxide or sul- 

 phuret. 



In concluding, I again readily acquit you of any intentional 

 misrepresentation ; for the carelessness you have repeatedly 

 evinced is quite sufficient to account for the errors you have 

 committed. Your obedient servant, R.Phillips. 



Article IV. 



Telescopical Observations on the Moon, 

 By the Rev. J. B. Emmett. 



(To the Editors of the Annals of Philosophy.) 



GENTLEMEN, 



The moon was one of the first objects examined by the tele- 

 scope. Galileo perceived so striking a resemblance to that 

 appearance which the earth may be supposed to have, if viewed 

 from a great distance, as to conclude, according to Anaxagoras, 

 Pythagoras, and other ancient philosophers, " Lunam sciHcet 

 esse quasi tellurem alteram, ejus pars lucidior terrenem super- 

 ficiem, obscurior vero aqueam congrue reprsesentet." (Sidereus 

 Nuncius, p. 17.) Galileo not only observed mountains, but 

 measured the altitudes of some ; and assigns a reason why he 

 could not perceive any upon the limb (p. 22, 23); had his tele- 

 scope been more powerful, they would have been distinctly 

 visible. Since this time, the speculations of philosophers have 

 been very various ; Hevelius retained the ancient opinion, and 

 supported it by many careful observations ; but at the present 

 day, astronomers usually maintain that the moon is destitute 

 both of water and of an atmosphere ; some making its surface 

 one mass of volcanic craters (Robison's Mechanical Philosophy, 

 p. 562) ; whilst others, in order to explain the origin of meteoric 

 stones, fancy that the moon is composed of the bases of alkalies ' 

 and earths in their metallic state ; by some unaccountable pro- 

 cess, masses of lunar matter are some how projected beyond the 

 point where the centripetal force of the earth is equal to that of 

 the moon ; continually descending, they reach our atmosphere, 

 inflame and descend to the earth ; these productions we mortals 



New Series^ vol. xii. z 



