GASES ABSORBED BY CHARCdAlv 259 



by charcoal expofed, for a greater or lefs length of time, to the 

 light of the fun j this enablecl me to afcertain the quantity of 

 ligiit and caloric which enter into the charcoal. 



XII. TThe experiments on atmofpheric air, which is more or 

 lefs abforbed according to its purity, follow next. 



XIII. After thefe are the experiments on different gafes, 



XIV. Oxigen gas gave me very fmgular refults, diame- 

 trically oppofite to thofe I had obtained in tubes hermetically 

 fealed, and when I pafled the charcoal through the mercury, 

 which deranged me greatly in the confequences I deduced 

 from it, 



XV". After this article will follow fome confiderations on 

 the quality of the charcoals madeufe of, which prove that their 

 property of abforbing is different according to their different 

 qualities. 



XVI. I afterwards ihow that my Inftrument may beufed in 

 many cafes, if inftead of mercury, coloured water is employed, 

 but with requifite modifications. 



XVII. The charcoals which had been employed in the ex- 

 periments all acquired a greater weight : I endeavoured to 

 extra6t the air which they had abforbed. 



XVIII. I alfo mention the trials which may be made by 

 faturating the charcoal with different fubflances, having only 

 made four experiments. 



XIX. I then proceed to the conclufion, in which I endea- 

 vour to give the explanation of thefe experiments. The opi- 

 nion which I had adopted in the fecond memoir, receives ad- 

 ditional confirmation from it ; but the refults of the experi- 

 ments I made on oxigen gas havihg changed the ideas I had 

 formed, I am not willing to hazard an explanation at prefent. 

 Philofophers will therefore be contented with having newfaCls 

 and new experiments. 



The experiments which I detail were repeated feveral times, 

 and their accuracy may be depended on, as I can affure my 

 readers, that I have always confidered truth as the brightefl 

 ornament of a philofopher. 



Experiments ffiade with my new Inftrument. 

 Ifl, The charcoal which I generally employed was that of Experiment! 



beech-wood ; the weight of the pieces half a dram, that is to ^^^^ ^^"^ "*^^ 

 g- .1 ' , r ■ inftruaicnfc. 



lay, thirty-Iix grams. 



S 2 2d. The 



