422 TRANSACTIONS OF THE 



• 



Mr. Tillman. — "Tanning" is the process of chemically combining gela- 

 tine with tannin. 



Tannin being an astringent, has a tendency to close the pores of the siin 

 at the first contact, and thereby to shut up the innumerable avenues through 

 ■which it should enter the substance of the hide, and, therefore the applica- 

 tion of hot liquor to the skin effects the desired chemical action more 

 rapidly at the surface, but produces a less pliable and a less durable leather. 



As the skin during its growth has been constantly subject to the animal 

 heat, it would seem reasonable to apply the tan liquor at a blood-heat. 



Most patent chemical compounds for opening the pores of skins are 

 worthless, because they, to some extent, destroy the fibrous texture of the 

 skin. 



In tanning it seems very important to "handle " the skins a great deal 

 during the process. So we may say that the three essentials required to 

 tan hides into leather, are, tannin, time and motion, the time and motion 

 being inversely to each other. 



The Chairman remarked upon the superior quality of the ink used in 

 the olden times, and instanced an old Denmark manuscript, which excited 

 our surprise at the intense beautiful black of its ink, 



Mr. Coryelle stated that ordinary black ink is much improved by being 

 boiled. 



Mr. Roosevelt read the remainder of his essay on Chemical Para- 

 doxes, remaining from previous evenings. This essay gave rise to an ani- 

 mated discussion on the various chemical theories propounded at different 

 times, and especially upon Mr. Roosevelt's one, given in the first part of 

 his essay. 



FIRE-PROOF BUILDINGS. 



The subject of the evening, "Fire-proof Buildings," being called up, 



Mr. Seeley considered that anything which is combustible cannot be 

 rendered entirely incombustible. We can only protract the burning of any 

 substance, but even in so doing we shall gain something of protection 

 against loss by fire. The results of the Carteron experiments seem to be 

 somewhat exaggerated. Silicate of potash and alum may serve as paints to 

 delay combustion by preventing the free access of oxygen to wood, &c., 



Mr. Meigs reminded the Association of the beautiful experiment on 

 the combustion of iron by means of an abundant supply of oxygen, as exhi- 

 bited during the war 1812, at Boston. A cannon, elevated about forty-five 

 degrees, received a white hob roll of sheet iron ribbon, which, as it passed 

 through the air, formed a long and powerful stream of flame, and the iron 

 was totally burned up. Rollsof this kind were called Carbonic rockets. 



Professor Hedrick stated that phosphate of magnesia is very incom- 

 bustible, and that it can be used as a covering paint or can be injected into 

 the pores of wood as a preventive of fire. 



Mr. Veeder had, as an extensive dealer in oils, observed a singular 

 loss of illuminating power in oils which had been much exposed to the 



