O/i Vegetal lorit 343 



i2ioiisness of experiments, and the pressure of other avoca- 

 tions) endeavoured to put the principal topics of the paper 

 alluded to in as concise a method as may be ; a species of 

 relaxation which, if you approve of, I may be induced to 

 repeat. The frequent similar labours of the enlightened 

 character I quote form so respectable a precedent towards 

 the like intent, that I am prone to trust the present will 

 not be regarded by you as less valuable for its want of ori- 

 ginahty on my part, inasmuch as the desire of diffusing 

 information forms the basis of my motives for forwarding 

 it^ an object not better to.be obtained than will be accom- 

 plished by an insertion in your valuable publication, a work 

 not less to be cherished as a national acquisition than the 

 plan and perusal of it nmst be gratifying to the public, and 

 among others to your obliged servant^ 



Kenniiigtor, Q, J. WrIGHT* 



Jan. 14, 1804. 



The substances which bear the 'greatest proportion, as 

 the constituent parts of plants (the ashes composing but a 

 fractional part) are water, carbon, hydroden, and oxygen, 

 of which the proportions are found to vary in difierent ve- 

 getables. 



V^an Helmont's experiment on the growth of a willow^ 

 which increased 6olb. in weight without diminution on the 

 part of the earth in which it vegetated, is well known, as is 

 also that of Duhamei, who observed the growth of an oak, 

 in water alone, for several years successively. Add to these 

 tlie numerous experiments of M. Tiliet, who sowe<i grains 

 of corn in various mixtiu'cs of sand, pounded glass, earths^ 

 Sec. without being able to distinguish between the grains 

 so produced, and those sown in the usual way 5 all which 

 experiments appear to set forth air and water as bcip.g the 

 matters essential to the nutrition of plants, and seem at the 

 same time to suppose the cH'ect of manures to be conlincd 

 solely to the retention of the humidity necessary to vegeta- 

 tion, the production of a slight degree of heat for th© 

 dasier developcment of the young plant, and. the more per- 

 iled division of the soil for the readier extension of the 

 radical tibres. 



'iliat the iiKirease of carbon in vegetables should be de- 

 rivetl from the mere ui(;dia air and water, appears, indeed 

 paradoxical; but Tjllet's experiments to ascertain the fact 

 are mconclusive, being conducted in perforated pots buricd 

 in the ground. 'J'hc Bame processes, repeated by Hassen- 

 ijratz, m insulated and unperiwralcd vessels (that is_la say,- 

 ^ under 



