Chemical Procrfs of VitaHtj. 36 j 



'with fimple combinations, and afterwards proceed to combinations of two, three, and four 

 principles. 



I have fent to the National Inflitute a memoir on the nature of light, and its chemical 

 •combinations. Mr. Wedgwood pretends that the phofphorefcence of calcined bodies is 

 not altered in hydrogene and azotic gas. I think he did not purify thefe gafes by means 

 of phofphorus, as I did. I have feen luminous wood extinguiflied in the azotic and hydro- 

 gene gafes. A fmall quantity of oxygene, being admitted into the veilel, caufes the whole of 

 the phofphorefcence * to revive. I have alfo converted morilles (Phallus Efculentus) into 

 a fubftance which refembles tallow, by means of the fulphureous acid. I have made foap 

 of it. 



Bap-eiilh, December 29, I;'9'5- VoN HuMBOLDT. 



Extracl of a Letter from Citizen FoVRCROT to Citizen V.iN JIIONS on the Suhjecl of that of 



Mr. Humboldt. 



I THINK Mr. Humboldt proceeds with rather too much expedition in his folutions. It 

 is to be feared that he may find it neceflary to retraft. I am apprehenfive that he admits . 

 too many hypothefes f : that he does not repeat each experiment fufficiently before he 

 forms a conclufion. This in particular is much more important with regard to the philo- 

 fophy of animal bodies than any other branch of fcience, becaufe it is furrounded by num- 

 beilefs difficulties and multiplied fources of error and illufion. I fear that if certain chemifls 

 continue to advance with fuch rapidity, the phyficians will foon have reafon to exclaim 

 againft this encroachment. If applications be too fuddenly made, and arbitrary fuppofitions 

 accumulated, it may perhaps come to pafs that this fcience may a fecond time be rejefled 

 from the healing art, as it was formerly by Stahl and Boerhaave, in confequence of the 

 excedive abufe of hypothefes committed before their time in this refpeft by Tachenlus, 

 Willis, and others. Too much earneftnefs may be equally pernicious to chemiftry as 

 well as medicine, and impede the progrefs which the firft is capable of producing, and 

 ought to produce, in the fecond. 



MelTrs. Girtanner and Valli appear to me to make an ill ufe of their abilities and know- 

 ledge in tills refpe^l. They fufler themfelves to be carried away by the ingenious notions 

 they derive from modern chemiftry. 



Ail this, however, does not prevent my being of opinion that the experiments of Mr. 

 Humboldt arc extremely intercfting, and that he ought to continue them with affiduity ; 

 but I (lioulJ wiQi that he would vary them more, repeat each in particular more frequently, 

 and be moderate in his conclufions. I cannot, for example, repeat to you how many new 

 ideas and chemical explanations, very probable in thcmfclvcs, have occurred to me during 



^ Spallanzani obfcrvcd tlic fame phenomena ; and, what is mure remarkable, he obfcrved the phofphoric or 

 fliining animals ccafid to emit liyht in the aiotc, hydrogene and c-irbonic gafes, and th« they emitted a light 

 infinitely more vivid in oxygene gis than in the atmofpheiic air. Chimico Efamc degli Efpcrimcnti de Goctt- 

 ling. M'idena, i7i)5. 



t For example,, in ibc prcccjing memoir hefpejksof the aiote 9f alkalis as if it were dcraoaftratcd tiiat 

 aiotc it one of ilic piincif le> of thtfe budics. I firrt announced or fufiit^lca this eight years ago, but it is not 

 jtt proved, f . 



3 A 2 fcveral 



