iv.] YEAST. 73 



physician, Van Helmont, lived in the latter part of the 



sixteenth and the beginning of the seventeenth century 



in the transition period between alchemy and chemistry 



and was rather more alchemist than chemist. Appended 



to his " Opera Omnia," published in 1707, there is a very 



needful "Clavis ad obscuriorum sensum referandum," in 



which the following passage occurs : 



" ALCOHOL. Chymicis est liquor aut pulvis summ subtilisatus, 

 vocabulo Orientalibus quoque, cum primis Habessinis, familiar!, quibus 

 cohol speciatim pulverem impalpabilem ex antimonio pro oculis tin- 

 gendis denotat. . . Hodie autem, ob analogiam, quivis pulvis teuerior, 

 ut pulvis oculorum cancri summd subtilisatus alcohol audit, baud 

 aliter ac spiritus rectificatissimi alcolisati dicuntur." 



Similarly, Eobert Boyle speaks of a fine powder as 

 " alcohol ; " and, so late as the middle of the last cen- 

 tury, the English lexicographer, Nathan Bailey, defines 

 " alcohol " as " the pure substance of anything separated 

 from the more gross, a very fine and impalpable powder, 

 or a very pure, well-rectified spirit." But, by the time 

 of the publication of Lavoisier's " Traite Eldmentaire de 

 Chimie," in 1789, the term "alcohol," " alkohol," or 

 " alkool " (for it is spelt in all three ways), which Van 

 Helmont had applied primarily to a fine powder, and only 

 secondarily to spirits of wine, had lost its primary mean- 

 ing altogether ; and, from the end of the last century 

 until now, it has, I believe, been used exclusively as the 

 denotation of spirits of wine, and bodies chemically 

 allied to that substance. 



The process which gives rise to alcohol in a saccharine 

 fluid is known to us as " fermentation ;" a term based 

 upon the apparent boiling up or " effervescence " of the 

 fermenting liquid, and of Latin origin. 



Our Teutonic cousins call the same process " gShren," 

 "gasen," "goschen," and "gischen;" but, oddly enough, 

 we do not seem to have retained their verb or their 



