Polytechnic Association Proceedinos. 843 



From these the percentage of sugar iu the latter was calculated; 

 it was found to be 1.45 per cent. What is the cause of that sweet 

 principle ? We will try to answer this question. In freezing and 

 thawing, the sap of the potato bursts the cells and thus puts au 

 end to vitality; at the same time decomposition is setting in, wliich, 

 though retarded by the cold, will nevertheless not be arrested 

 entirely — the more as the atmosphere at this time, especially 

 during snow-falls, always abounds in that powerful oxydizing 

 agent, ozone. No doubt that the albuminous matter which is con- 

 tained in the outmost layer of the starch grains will first be attacked 

 by it; and is it not very probable that they will thus be transformed 

 into that peculiar substance called diastase, a body which as we 

 know possesses the same power as dilute acids of converting a 

 proportionally larger quantity of starch, first into dextrine and 

 then into sugar, when exposed to a temperature of from 140 to 

 169° F.? This is completed in cooking. Wheat probably contains 

 enough diastase, as every seed does when sjjroutiug, to convert all 

 its starch into dextrine and sugar; not so the potato, but still it con- 

 tains enough to form so much sugar as to give it that well known 

 peculiar sweet taste. Adjourned. 



January 30, 1868. 

 Prof. S. D. Tillman in the chair. 

 The Chairman presented the following notes on science: 



■ BLACK PEPPER. 



The black pepper tree has been brought to bearing maturity in 

 California. 



VOLCANIC FLAMES. 



Janssen, by spectroscope analysis, has found that the flames of 

 the volcano at Santorin, give evidence of the presence of sodium, 

 hydrogen, copper, chloride and carbon. 



KEW COLLODION PAPER. 



Obernetter, of Munich, has brought a silver collodion paper in 

 the market, far more sensitive than ordinary silvered albumen paper, 

 which makes it of more service to the photographer during the 

 winter months. 



