[ '53 ] 



As to the coal or carbonaceous principle whicli this willow 

 muft alfo have contained, it is probable that much of it exifted 

 in the earth in which the willow grew ; fome is contained in 

 all moulds or vegetable earth, and as we are not told what fort 

 of earth Van Helmont ufed, we may well fuppofe it was good 

 vegetable earth, its quantity amounting to 20olb. This principle 

 may alfo have been contained in the water, for the purcft rain 

 water contains fome oleaginous particles, though in an exceeding 

 fmall proportion, as Mr. Margraaf has obfervedf , and all oil con- 

 tains coal. Some alfo may have pafTed from the furrounding 

 vegetable earth through the pores of the earthen vefTel, All 

 the other experiments, adduced to prove that water is the fole 

 food of plants, may be explained in the fame manner. Grains 

 of wheat have been made to grow on cotton moiftened with 

 water; each produced an ear, but that ear contained but one 

 grain*. Here the carbonaceous fubftance was derived from the 

 grain and afterwards difFufed and tranfported through the whole 

 plant by the water abforbed ; for it muft be obferved that grain, 

 like an egg, contains much of the nourifhment of its future ofF- 

 fpring — it is thus that tulips, hyacinths and other plants, expand 

 and grow in mere water. 



The earth contained in rain-water is united partly with 

 tlie nitrous and marine acids, as Margraaf has fhewn, but far 

 the greater part only with fixed air; for the feeble traces of 

 the two former acids could not hold in folution the loo grains 

 of earth which he found in 30olb. of rain-water. 



Vol. V. U Br 



f 2d Marg. 15, 90. * 2d Young's Annals, 487. 



