On Calcarious aiid Gypjious Earths. 43 



depofit its water, earth, oils, and whatever other fubftancc is 

 found floating in it. If inflammable air is contained in a 

 receiver, and an ele£lric fpark pafTed thro' it, it may be made 

 to depofit a confiderable quantity of water, which is always 

 combined with it. In this way then oils and even earth may be 

 fupplied, for it is certain that the water contained in the atmof- 

 phere poflefles a portion of earth, and perhaps no other earth 

 but this is fufficiendy atinuated to enter the abforb&nt vefl'els 

 of plants. Thus a gallon of rain water diflilled, yields about 

 lixty grains of Calcarious earth, which accounts for the encreafe 

 of certain plants without either earth or water, and which are 

 ftill found to contain both. Should it be denied that the 

 attra6lion of the heat from the atm.ofphere is capable of decom- 

 pounding it, it will neverthelefs be admitted that there are 

 an infinite variety of vapours which are exhaled by the fummers 

 fun, which owe their levity to heat only, and not being perma- 

 nently elaftic, mufl: fall when the heat is attra6led from them. 

 Thence the fertility occafioned by dews impregnated as they 

 always are with a variety of heterogeneous fubflances ; fuch of 

 thofe vapours therefore as float near the earth's furface (and 

 thofe will be mofl; fertile) will fuddenly be condenfed by any 

 extraordinary degree of cold, which the folution of the fait I 

 have mentioned may occafion. But the effe6l of the Calcarious 

 earth does not flop here ; it is not fatisfied with a fingle opera- 

 tion, but like a faithful fl:eward flill exerts itfeJf for the fupport 

 of the vegetable family committed to its care. This earth, when 



