NUTKITION OF VEGETABLES. ly 



very Hack colour, ^md in little shinin*^ scales. Scarcely 

 any vapour arose from it when throvvi) on burning coals, and 

 1 consider it as charcoal well saturated with hidroj^en. Art 

 nmy imitate this substance, by effecting by fire what nature 

 does by time. If we deprive a vegetable substance of al- 

 most all its oxigen, and a small quantity of its hidrogen, by 

 exposing it to a certain temperature, the result will be a hi- 

 droguretted charcoal, partly soluble in potash, as I have 

 found by experience. 



That part of the mould, which had resisted the action of The residuum 

 potash, weighed when dried 5 gr. It had no longer the phy- ^0^1?'^^°*^ ^'*^' 

 sical characters of mould ; was in pieces that were tolerably ''l^ii 



hard and brittle; and had a striking resemblance to pitcoal, 

 which led me to produce it in larger quantity. In this way 

 it had still such a resemblance to coal, that I could com- 

 pare it to nothing else. 



From this examination of mould it appears, that it can- It afFords no 

 not supply plants with any soluble matter for their nutrition, ^^^"^^^ matter 

 since boiling water has no action on it. It would be super- 

 fluous to say, that seeds sowed in it vegetated with extraor- 

 dinary vigour; but I must not omit to mention the presence 

 of a large quantity of potash in the plants, though I could 

 not detect any in the mould in which they grew, by the most 

 strict researches. 



These observations appear to corroborate the opinion of Manure thcre- 

 Tillet and Parmentler, who consider manure as useful only ^""^^^ seems to 

 by retaining moisture, and keeping strong soils open for by retailing 

 some time, so as to allow the roots of plants to penetrate "Jointure. 

 them. But if water and air be the only sources of the food 

 of plants, any insoluble matter, sufficient in quantity, and 

 duly watered, must be adequate to the purpose of their 

 growth. This I endeavoured to ascertain by experiments. 



Exp. I. In a box tilled with pure litharge I sowed 400 Mustard seed 

 seeds of white mustard, weighing 2*2 gr. These I watered -o^^" '" ^i- 

 frequently and carefully with distilled Avater. The box was ^^^^^^' 

 placed in a good aspect, and a glass was hung over it to 

 keep out the dust. The plants throve very well, and pro- 

 duced perfect pods. I collected all the seminal leaves as 

 well as the rest that dropped off; and when the vegetation 

 was at its height, pulled up the plants. Having well washed 



Vol. X VIII— Sept. I807. C the 



