WINE-MAKING IN CALIFORNIA. 287 



The lowest figure for acid (.49) is given by Nos. 556 and 

 558, the hot fermentation with cover, and by the one with 

 the three submerged frames. In the case of the latter this 

 was to be looked for, and is precisely one of the chief advan- 

 tages claimed for Ferret's method. In the case of the former 

 it is somewhat unexpected, and is the more instructive in con- 

 trast to No. 557, the hot fermentation in which no cover was 

 used, and in which the acid is one pro-mille higher. Almost 

 precisely the same difference occurs in the fermentations made 

 at the lower temperature, one with the floating cover on (No. 

 561) and the other (No. 560) without cover. The beneficial 

 influence of the cover in preventing the formation of acid 

 during fermentation is therefore placed beyond question. 



It should, however, be added, that in none of the fermen- 

 tations made, there is at this time (November 24), a notable 

 amount of volatile (acetic) acid. This is true even of No. 

 564, the "old-style" one, in which the odor of vinegar was 

 abundantly obvious before ' pressing. It shows the odor of 

 vinegar plainly in boiling, but the amount is at present less 

 than five thousandths of one per cent. 



It is somewhat remarkable that the fermentation of 562, 

 made at the lowest temperature, should yield a relatively 

 high proportion of acid, .exceeding that found in the fermen- 

 tation made under the same conditions at a higher tempera- 

 ture. Whether this is to be accounted for by the longer 

 duration of the low-temperature fermentation, remains to be 

 investigated. 



TANNIN. 



Considering, next, the matter of tannin, we- note at a 

 glance the influence of the high temperature in aiding a com- 

 plete extraction. The two hot fermentations, Nos. 556 and 

 557, have given the maximum of tannin, despite their short 

 duration; more even than in the case of the tank with dili- 

 gent open foulage, and as much as the Morel process, stems 



19 



