Proceedinos of the Polytechnic Association. 891 



of a furnace for three hours. It will locate a leak in the boiler by 

 moisteninp: the place. It expands about the same as iron. One 

 hundred and fifty square feet, two inches thick will weigh 600 pounds. 



Dr. D. D. Parnielee remaked that there was no better non-con- 

 ductor of heat than plaster of Paris. The best way he found to use 

 it was to saturate old newspapers with the plaster of Paris, and 

 wrapping them around the pipe or boiler. Paper coated with plaster 

 of Paris cannot be made to burn with a flame. 



Mr. Norman Wiard said that Mr. Snyder's method of coating pos- 

 sessed the advantage of being a non-conbustible material (Mr. W. 

 exhibited some of the belting used on the boilers at the fair, which, 

 after a few days use, were converted into black charcoal). He had 

 seen belting take lire of itself, and the engineer of the steamer 



St. John told him that on his boat it took fire twice. 



Adjourned. 



December 9. 1869. 



Prof. S. D. Tillman, in the chair; C. E. Emery Esq., Secretary. 

 The chairman presented the following scientific notes : 



Heat as a Measure of Chemical Decomposition. 

 M. Thomsen has a paper in Poggendorff'-s Annaleii on "Thermo- 

 chemical Researches," the purport of wdiich is that different acids, 

 when neutralized by the feame base, evolve unequal quantities of 

 hoiit. "When, therefore, any acid displaces another acid from its com- 

 bination with that base, this decomposition will be accompanied 

 either by an evolution of heat or by an absorption of heat, according 

 to the greater or less heat of neutralization possessed by the free 

 acid or the acid of the salt. The quantity of heat thus evolved or 

 absorbed affords a measure for the degree of decomposition. 



The Solar Corona. 

 The result of the numerous observations of the Corona, made by 

 American scientists during the late solar eclipse, are thus briefly 

 summed up by a correspondent of The Yale College Courant: They 

 demonstrate concerning the Corona: 1. That it is not flame, since the 

 spectrum exhibits no dark lines. 2. That it is not reflected light, 

 ^', 6'., light emanating from an incandescent body, and reflected by 

 the particles of its atmosphere, because it is in no degree polarized. 



