( 84°) 
it to their own substance, reproduce their species 
and maintain an existence of longer or shorter dura- 
tion. Thus far the learnedare agreed, but at the: 
next step they differ. 
What is this food that gives: to: plente: their deve- 
lopement, and’ maturity; and powers of reproduc- 
tion? Lord Bacon believed that water was the source — 
of vegetable life, and thatthe earth was merely its 
home, its habitation, serving to keep plants upright 
andito. guard them against the extremes of heat and: 
cold. ‘Tull; on the other hand, (and after him Du: 
Hamel) pronounced pulverized earth the only pabu- 
lum of plants, and on this opinion built his system of 
husbandry. Van Helmont and Boyle opposed this 
doctrine by experiments: the former planted and 
reared a cutting of willow ina bed of dry earth care- 
fully weighed and protected: against accretion by a 
tin plate, so perforated as to admit only rain and 
distilled water, with which it was occasionally mois- 
tened. At the end of five years the plant was found: 
tohaveincreased one hundred and sixty-four potnds, 
andthe bed of earth to have lost, of its original 
weight, only tivo ounces. Boyle pursued a similar 
process with gourds, and with a similar result.. Not- 
withstanding the. apparent conclusiveness of these 
experiments, their authority was shaken, if not sub- 
verted, by others made by Margrafi, Bergman, 
Hales, Kirwan, &c. &c. The first of these shewed, 
that. the. rain. water, employed by Van: Helmont, 
was itself charged with saline and other earthy mat- 
ter; Bergman demonstrated this by analysis, while 
Kirwan and Hales proved that the earth, in which 
