PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 483 



mordant. In calico printing it fixes the colors with which it com- 

 bines, and renders them comparatively imperishable. It is cm 

 ployed to preserve size — a gelatinous body, prone to decay. It 

 as used to keep hides from spoiling. In short, it is an agent 

 which, when it combines with albumenic substances, render them 

 relatively insiisceptijble of chemical change. Such a body, in 

 solution m the blood, would combine with the albumenic sub- 

 sta,nces all tiie more readily from the alkaline character of the 

 fluid — which, freeing the alumina from the air, would precipitate 

 it upon the allnnnenoid compound. These bodies, tallen within 

 the grasp of the alumina, would be incapable of further change, 

 and their otfice in assimilation impaired, if not at an end. 



Beside the effect of alumina in withdrawing phosphoric acid 

 from the stores of nutiition received with it into the alimentary 

 canal, and deleterious effects on assimilation, when received into 

 the stomach either as alum or as hydrate of alumina, there is the 

 better known effect upon the mucous membrane of shriveling, 

 which is accompanied by constriction of the capillaries, congestion 

 and sometime by inflammation. In tatal experiments made upon 

 animals, the mucous membrane has been found extremely inflamed. 



In view of these effects of alum, it is obviously wise to leave the 

 use of such an agent in the counsel of educated physicians, 



Thb Effect of Sunshine on Fire, by Piiof. E. N. Hosefoed. 



Professor Horsford commenced by alluding to the popular 

 notion that sunshine deadens fires; mentioning that the fires in 

 grates in rooms having southern exposures, burn briskly in the 

 early part -of the day, «lacken before noon, and revive again to- 

 wards sunset. Stoves and ranges that bake well in the autumn, 

 winter, and spring, fulfill their office but indifferently in the mid- 

 dle of the day in the height of summer. Some furnaces in which 

 iron is generally smelted without difficulty, cannot, in very hot 

 terms, be brought to a working heat. While the popular mind 

 ascribes these effects to some agency of the sun, scientific men are 

 disposed to regard the effects as rather apparent than real. 



The first recorded research bearing upon the subject was made 

 as long ago as 1825, by Dr. Thomas McKeever, who found, as he 

 conceived, the popular impression sustained. In his experiments 

 a given weight of wax taper was consumed quicker in the dark 

 than when exposed to the sun. A given length of candle required 

 less time for combustion in the dark thaai in the sunshine. A given 



