261 WAtf£fi in muriatic Acta gas. 



lectness cf Colonel Murlge's operations, both general and par- 

 ticular $ and of the extreme rashness with which Don Rodri- 

 guez has affirmed, that " it is very evident .that the zenith dis- 

 tances of* stars taken at Arbury Hili are affected by some con- 

 siderable error ." The matter in question might, as you will 

 1 perceive, have been settled in narrower compass ; but the cele- 

 brity of the institution under whose auspices the Don's animad- 

 versions are circulated, seemed, in some measure, to call for a 

 tolerably full reply to his paper. 



For the reply here presented, the public must consider me 

 alone as responsible : and I trust that when the two papers have 

 been compared, I shall not be thought to speak incompatibly 

 with the courtesy due to a foreigner, or the respect dirc to a 

 brother mathematician, when I say that Don Rodriguez has 

 completely failed to establish the point, respecting which he 

 ought to have felt certain before he commenced his strictures. 



OLINTHUS GREGORY. 



Royal Military Academy, 

 Woolwich, March 5th, 1813. 



IV. 



On the Existence of comlihcd Hater in muriatic acid Gas. By 

 J. Murray, Lecturer on Chemistry, c5"c. Edinburgh. 



To Mr. Nicholson. 



Edinburgh, March 3, 1813. 

 SIR, 

 Late experi- 1TN your Journal for January, an account is given of an ex- 

 H e Da°v Sh -**- P eriment performed by Sir Humphry Davy in the College 

 Laboratory of Edinburgh, in relation to the question on the 

 existence of combined water in muriatic acid gas. I had found 

 that the salt formed by the combination of this gas with am- 

 monia, affords water when it is exposed to heat ; and this water, 

 I inferred, is derived from the acid. Sir H. Davy supposed it 

 to be water which the salt had absorbed from tie air • and he 

 and his brother affirmed, that when the air is excluded, none 

 is obtained. I resumed the investigation, and found that the 



salt 



