112 On the Mean Density of the Earth. 



azote is obtained, and that this azote is cither disengaged 

 from the meat, or the oxygen is converted into azote. 



10. When the nieai begins to corrupt in the hydrogen, 

 there is disengaged from it carbonic acid ; but when putre- 

 faction did not take place, none of it was formed. 



11. That upon the meat in oxygen gas are formed small 

 drops of water, which resemble the pustules of the small- 

 pox. 



My next researches shall be directed to ascertain all these 

 facts I have announced, and especiallv to satislv myself, if 

 the carbonic acid gas found in the hydrogen exists in the 

 meat; to determine the influence of light^ and the shining 

 properties of putrid meat. 



XXV. Letter from Dr. Hutton on the Calculations for 

 ascertaining the Mean Density of' the Earth. 



To Mr. Tilloch. 



Sir, x\.ccustomed, as I constantly am, to peruse with 

 much pleasure and profit, the numerous valuable philoso- 

 phical dissertatioi>s that adorn your Magazine, I am truly 

 sorry to have occasion to make a remark on a paragraph in 

 your Number for the month of June last, which has not 

 done justice to my labours, and which has doubtless been 

 admitted unawares into your work ; as I cannot for a mo- 

 ment suppose it possible, that either yourself or Mr. Davy 

 would intentionally write or say one word to do injustice 

 or to give pain to me or to any one else. The paragraph 

 alluded to is in your excellent account of Mr. Davy's very 

 ingenious Lectures on Geology, given at the Royal Institu- 

 tion, being in page 469 of your last volume ; and runs thus : 

 *' But what are the agents concerned in these great and 

 awful elevations ? The discoveries of Mr. Davy prove that 

 the earths and alkalies consist of metals united to oxygen, 

 or pure air; and these metals are highly inflammable, some 

 of them so much so as to burn even in contact with w ater. 

 The mean density of the earth, as determined bv Mr. Ca- 

 vendish and Dr. Maskelyne, would lead to the conclusion 

 that the interior consists principally of metallic matter, 

 which may be alloys of the metals of the earths and alkalies 

 with the ccnimon metals: — and such an assumption, says 

 Mr. Davy, would ofitr a ready explanation of subterranean 

 heat and volcanic explosions ; for, supposing water from 

 the sea or lakes to act upon these inflammable masses, elastic 



matter* 



