27 8 Mr. Henry on Ferments and Fermentation. 



cyder. An old gentleman, to whom I gave 

 a half pint glafs full of it, called out in raptures 

 to know what delicious liquor he had been drink- 

 ing, and earneftly defired that, if 1 had any more 

 of the fame, 1 would give him another glafs. 



Dr. Prieftley, as has been already mentioned, 

 had inforined us that fixed air, thrown into wine 

 or malt liquor, grown vapid, rellored to them 

 their brifknefs and pleafant taile. On impreg- 

 nating fome vapid ale with fixed air, I was dif- 

 3ppointed in not finding the effedl, immediately 

 produced. But after bottling the ale and keep- 

 ing it ciofely (lopped for four or five days, it was 

 become as brifk. as ale, which, in the common 

 way, has been bottled feveral months. 



In the year 1778 1 impregnated, with fixed air, 

 a quantity of milk whey, which I had clarified 

 for the purpofe of preparing fome fugar of milk, 

 and bottled ic. In about a week, the whey in 

 one of the bottles, which had been fo loofely 

 corked, that the liquor had partly oozed out, 

 was remarkably brifk and fparkling. Another 

 bottle, which was not opened till the fummer of 

 1782, contained the liquor, not in fo brifk a 

 ftate, but become evidently vinous, and without 

 the lead acidity, perceptible to the tafte. 



I now began to fufpeft that fixed air is the 

 efficient caufe of fermentation ; or, in other 

 words, that the properties of yeaft, as a ferment, 

 depend on the fixed air it contains; and that 

 yeaft is little elfe than fixed air, enveloped \t\ 



the 



