French National Instifitie, 177 



silex be dissolved, and absorbed by ibe plant ? How could 

 it circulate m the sap ? For all this must have been neces- 

 sary before it could be deposited in the knots of the stem. 

 Messrs. Fourcroy and Vauquelin are of opinion that potash 

 has served as the solvent, and that it has carried with it into 

 the sap these particles of si'ex. According to them, there- 

 tore, talasheer proves nothing in favour of those who be- 

 lieve that silex can be produced merelv by the act of vege- 

 tation. 



These indefatigable chemists have carried their researches 

 to a phaenomenon of disease in vegetation, interesting by 

 its sinoularitv, and long known by the damage it occasions. 

 They have endeavoured, in consequence of a memoir pre- 

 sented to the Institute by M. Girod-Chantrans, to deter- 

 mine the nature of the stnnt in wheat. They have found 

 in it an oil of a green colour and of the consistence of but- 

 ter; phosphoric acid, in part combined with magnesia, and 

 lime, and ammonia; charcoal, and a veaeto-aninial sub- 

 stance perfectly similar to thai produced by the decomposi- 

 tion of the gluten of wheat bv putrefaction. They thence 

 conclude that the smut is a residuum of farina decomposed 

 by putrid fermentation, and suppose that it arises from a 

 superabundance of animal manure, and a too hot and moist 

 temperature at . '.e time of sowing, or when the grain is in 

 flower. If agriculturists should ackno^.Iedge that these 

 Circumstances determine in reality a greater quantity of 

 smut, it might be possible to prevent, in some cases, this 

 scourge. 



Messrs. Fourcroy and Vauquelin have analysed likewise 

 a mould found at the depth of more than fifty feet in some 

 desert islands of the South Seas, and which is employed as 

 manure on the coasts of Peru, where it is called guano. 

 This analysis has so great a resemblance to that of pioeons' 

 dung, that there is reason to believe, with Mr. Humboldt, 

 who brought this gvana to Europe, that it is nothing but 

 the excrement of birds, which frequent these islands in im- 

 mense numbers. 



Ttiis substance, as may be seen, is an object of very li- 

 miied utility; but chemistry has long endeavoured to pro- 

 cure one to agriculture which would l)e of more uuiversaj 

 importance, nan)ely, suo-ar extracted from indigenous plants. 

 We gave an account, at The time, of the efi'orts of M. Achard, 

 of Berlin, to obtain it from beet-root. M. IVoust, a celc- 

 lebrated Spanish chemist, has extracted it from grapes; he 

 has given a detail of the whole process in a memoir sent to 



Vol. S2. No. SC. July 180j. M US 



