588 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



cities with pure compressed air, will confer a more lasting favor even than 

 those who furnished the water; the whole social, commercial and manufac- 

 turing system will be improved, and health, comfort and longevity will be 

 the blessings bestowed on the present generation, while tlie cliildren in- 

 stead of taxing their poor weak brains in badly ventilated and worse 

 heated school houses, will enjoy the pure country air whilst they improve 

 the better facilities offered in cities for education. If our efforts could 

 hasten the time when all this will be accomplished by but one year, we 

 would feel amply compensated by the consciousness of having saved hun- 

 dreds of human beings from an untimely grave. 



The Chairman briefly commented on the law of Mariotte, that the pres- 

 sure of an elastic fluid, at a constant temperature, varies inversely as the 

 space it occupies, and directly as the density. 



" The necessity of a reform in our weights and measures," was selected 

 as the subject for the next discussion. 



Adjourned. 



Ameeican Institute Polytechnic Association,) 

 March 3c^, 1864. j 



Chairman, Prof. S. D. Tillman; Secretary, Mr. B. Garvey. 

 After some desultory conversation on the value of an invention which is 

 to be subjected to further test, the Chairman presented the following sum- 

 mary of scientific news: 



New Explosive Compound. 



If glycerine, a liquid obtained from fats, is treated with nitric and sul- 

 phuric acid as cotton is treated to produce gun-cotton, the product when 

 heated explodes with great violence. This compound has not been applied 

 to any useful purpose. It is a powerful poison, one drop taken into the 

 human stomach being sufficient to produce death. 



The Chairman remarked that as glycerine may yet be applied in many 

 branches of the arts, it would be proper to examine its chemical character- 

 istics. It is a sweetish liquid composed of six equivalents of carbon, eight 

 of hydrogen, and six of oxygen. As grape sugar consists of twelve of 

 carbon, twelve of hydrogen, and twelve of oxygen, it will be seen that gly- 

 cerine has half the number of equivalents of each element, plus two of hy- 

 drogen. It is a base which, combined with three equivalents of acid, forms 

 the neutral fats olein, stearin, margarin, palmatin, &c. These, when uni- 

 ted with soda or potash, saponify; the acid unites with the alkali, forming 

 soap, while the weaker base, glycerine, is set free. In many of our large 

 soap-making establishments the glycerine is not saved or applied to any 

 useful purpose. 



Mr. John E. Gavit stated that it was now manufactured largely in Phil- 

 adelphia. It has been found very useful when mixed with glue for prin- 

 ters' rollers. He had also used it instead of soap and water, in the opera- 

 tion of engraving engines. Its price is about $1.50 per pound. 



Mr. Garvey said that ink-rollers sometimes are spoiled by a heated and 

 moist atmosphere, and inquired whether the glycerine mixture was thus 

 affected. 



