DESCRIPTION' OF A NITRE CAVE. 247 



M. Turgot, the celebrated M. Lavoisier was appointed super- 

 intendant of the French national powder works, and with what 

 success he executed the duties of his important commission the 

 history of their subsequent naval campaigns have sufficiently 

 evinced. The efforts of European chemists, seem to have been 

 principally directed to the removal of the marine salt which 

 the nitre of Spain and India contains in great quantities. In 

 the nitre of Kentucky, I have never detected a particle of that 

 salt, and I am confident, that if any is found in it, the pro- 

 portion must be very inconsiderable indeed. The rock salt- 

 petre I am persuaded, would, with very little refinement, make 

 gun-powder capable of retaining its efficient properties during 

 the longest voyages, as I have never discovered, in that species 

 of nitre, the smallest tendency either to deliquescence or efflo- 

 rescence. 



It will be observed, that I have not in this paper, hazarded 

 any opinion with regard to the formation of nitre in our sand 

 rocks. I freely confess that I have no theory on that subject 

 which is satisfactory to my own mind, I am even disposed to 

 suspect, that our greatest chemists have still much to learn with 

 regard to this salt, so valuable in time of peace, so indispensa- 

 ble in time of war. 



No. XL. 



An Essay on the vermilion colour of the blood, and on the different 

 colours of the metallic oxides, with an application of these prin- 

 ciples to the arts. By Samuel F. Conover M. D. 



Read June loth, 1S0&. 



On the Vermilion colour of the blood. 



THESE subjects have excited the attention of some of the 

 most eminent philosophers of the last and present century, 

 though little progress was made in the explanation of these phe- 

 nomena, previously to the institution of the pnemnatic philo- 

 sophy, when truth burst forth upon mankind, dispelled the 



K 



