454 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



Mr. McWilliams. — I have more orders for my locks than I can fill, and 

 am busy enlarging my works, but as soon as I get time, I intend to bring 

 tne lock here and offer it for trial. 



Mr. Bull. — I should like Mr. Hobbs' opinion of that lock, for if it cannot 

 be picked I should like one on my front door. 



Mr. Hobbs. — That is a tumbler lock with false notches in the tumblers, 

 and possesses the same amount of security as all locks of similar construc- 

 tion. To pretend that such a lock is unpickable is simply ridiculous. I 

 have no doubt, however, that any well-constructed lock with four or more 

 notched tumblers is sufficiently secure for any sti'eet door. 



Adjourned. Thomas D. Stetsox, Secretary. 



American Institute Polytechnic Association, 

 February 6, 1863 



•\ 



The Chairman, S. D. Tillman, Esq., presiding. 



There being no miscellaneous business, the regular subject, "Heat," was 

 considered. 



The Chairman remarked that there was a very general but erroneous 

 opinion prevalent, with regard to what are called conductors and non- 

 conductors of heat. The latter term should not be used. All kinds of 

 ponderable matter will absorb, conduct and radiate heat. Solitls are better 

 conductors of heat than gases. These may be classified as slow and rapid 

 conductors. The late fire at the Cherry street bakery, in this city, illus- 

 trated what disastrous consequences may follow as the effect of slow con- 

 ductors. It was supposed that masses of brick work of immense thickness 

 would completely protect the wood work in contact with its outer surface. 

 But if the fire within is kept up without intermission for several weeks, 

 the whole mass becomes thoroughly heated, and the outside sufficiently so 

 to set fire to dry wood. There should always be constructed, in the out- 

 side portions of the brick work, open spaces through which air, a still 

 slower conductor, can circulate. 



Mr. Dibben remarked that he had long ago predicted that, with the 

 present fashion of building and driving cracker bakeries, they would all 

 be burned once a year on the average. He objected to the use of the term 

 " latent heat," as many persons arc thereby led to consider it as lost heat; 

 while, on the contrary, no heat is ever lost, although it might remain 

 apparently but slightly efficient. The force of heat may take another 

 form, for light, heat, electricity and magnetism are all convertible forces. 



Mr. G. Bartlett directed the attention of the meeting to another branch 

 of the subject, the amount of heat generated by burning gunpowder. He 

 gave some of the data necessary for comjjuting the effective force. A few 

 particles of the powder must be consumed, to warm the mass to be burned 

 to at least six hundred degrees; another portion is required to bring the 

 solids into the gaseous state. He then proceeded to show there were 

 several other elements to be included in arriving at a correct conclusion, 

 and, as these elements had not been definitely estimated, we must conclude 



