194 



MANURES. 



Sect. X. 2. 7. 



decompofing infoluble faline earths, as gypfum 



metallic fait 



as 



f 



and 



thus producing more foluble or innocuous falts. 

 And which laftly forms a part of the various vegetable productions of 

 fugar, honey, wax, refin, and other fecretions. 



7 



There is a curious evolution of oxygen attends the perfp 



of the leaves of plants, which is not known to attend that of animal 



lungs; 



and th 



is 



that when vegetable leaves are expofed to th 



fun's light, they feem to give up oxygen < 

 give up carbonic acid gas, like the breath of 



but 



animal lungs might do the fame, if they were expofed 



in the dark they 

 It is probable that 



to the lisht : 



as perhaps might be fubjedted 



periment 



the oills of fifli, or 



£> 



by breathing through a tube into water in the funfhinc. 



In refpiration as well as in combuftion fome light may poffibly be 

 given out as well as fome heat from the combination of oxygen with 

 fome phlogiftic bafe, as carbon or phofphorus ; whence the produc- 

 tion of carbonic and phofphoric acids in both animal and vegetable 



refp 



In moft anim 



th 



quantity of light is probably 



fmall to be perceived, if their bodies were tranfp 



but in the 



glow-worm of this country, ai 



the tropical climates, I fufpe(Sl: the light 



d in the more luminous fire-flies of 



to be emitted from th 



the a6t of refpiration, which is a flow combuft 



8. Befides the ufe of oxygen in 



th 



fp 



of 



o 



etabl 



when applied 



L 



mixed in the atmofph 



It IS 



believed by many to contribute much to their growth and nourifh 



ment 



combined flate, when abforbed by th 



d that 



by the decompofition of water in the vegetable fyflem, when the hy- 

 drogen unites with carbon and produces oil, the oxygen becomes fu- 

 perfluous, and is in part exhaled, as further fpoken of in Sed. XIII 



Hence alfo fome calciform ores, or metallic oxydes, as raddle, 

 and calamine, and burnt clay, are fuppofed to be ufeful as manures. 



I. 2. 



becaufe they contain much oxy 

 this Sedion. 



as mentioned in No. 7. i. 



of 



Mr 



\ «-, 



