522 THE POPULAR SCIENCE MONTHLY. 



concerning the manufacture of sherry, and learned that the grapes are 

 usually sprinkled with a little powdered sulphur as they are placed in 

 the vats prior to stamping. The quantity thus added, however, is 

 quite insufficient to account for the sulphur compounds in the samples 

 of wine I examined. Another source is described in the books — that 

 from the sulphuring the casks. This process consists simply of burn- 

 ing sulphur inside a partially-filled or empty cask, until the exhaus- 

 tion of free oxygen and its replacement by sulphurous acid renders 

 further combustion impossible. The cask is then filled with the wine. 

 This would add a little of sulphurous acid, but still not sufficient. 



Then comes the " plastering,' or intentional addition of g3^psum 

 (plaster of Paris). This, if largely carried out, is sufficient to explain 

 the complete conversion of the natural tartrates into sulphates of pot- 

 ash, but such plastering is admitted to be an adulteration or sophisti- 

 cation, and the best makers deny their use of it. I obtained samples 

 of sherry from a reliable source, which I have no doubt the shipper 

 honestly believed to have been subjected to no such deliberate plaster- 

 ing ; still, from these came down an extravagantly excessive precipi- 

 tate on the addition of chloride-of-barium solution. 



At last I learned that " Spanish earth " was used in the fining. 

 Why Spanish earth in preference to isinglass or white of ogg, which 

 are quite unobjectionable and very efficient ? To this question I could 

 get no satisfactory answer directly, but learned vaguely that the fin- 

 ing produced by the white of ^ig^y, though complete at the time, was 

 not permanent, while that effected by Spanish earth, containing much 

 sulphate of lime, is permanent. The brilliancy thus obtained is not 

 lost by age or variations of temperature, and the dry sherries thus 

 cooked are preferred by English wine-drinkers. 



Here, then, is a solution of the mystery. The sulphate of potash 

 which is thus made to replace bitartrate is so readily soluble that nei- 

 ther changes of temperature nor increase of alcohol, due to further 

 fermentation, will throw it down ; and thus the wine-merchant, with- 

 out any guilty intent, and ignorant of what he is really doing, sophis- 

 ticates the wine, alters its essential composition, and adds an impurity 

 in doing what he supposes to be a mere clarification or removal of im- 

 purities. 



I have heard of genuine sherries being returned as bad to the ship- 

 per because they were genuine, and had been fined without sophistica- 

 tion. Are we to blame the wine-merchant for this ? I think not. 



My own experience of genuine wines in wine-growing countries 

 teaches me that such wines are rarely brilliant ; and the variations of 

 solubility of the natural salt of the grape, which I have already ex- 

 plained, shows why this is the case. If the drinkers of sherry and 

 other white and golden wines would cease to demand the conventional 

 brilliancy, they would soon be supplied with the genuine article, which 

 really costs the wine-merchant less than the cooked product they now 



