LEATHER-MAKING. 361 



tan. Both were economical devices. The New England tanners 

 had long been accustomed to dry their spent tan during the sum- 

 mer and store it for winter use. It was then brought into service 

 to heat liquors, and in some cases to generate steam for general 

 tanning purposes. It was found, however, that nearly a half of it 

 was lost in drying. The result was, that attention began to be 

 given to the problem of utilizing it to greater advantage. In 

 1852 Joseph B. Hoyt conceived the idea that the wet spent tan 

 might be burned in a detached brick furnace. He made the 

 experiment at his tannery in Woodstock, Ulster County, N. Y. 

 After several trials he was successful, and got from the utilization 

 of this hitherto useless product enough power to drive his whole 

 machinery. Since the success of Mr. Hoyt a number of furnaces 

 have been devised for burning this wet tan. That of Mr. Hoyt, 

 as perfected by him, consisted of two pairs of ovens, each pair 

 being connected with three horizontal flue boilers. Each oven, 

 with its boiler, was independent of the other, and each had a 

 separate feed-pipe, steam-pipe, and water-tank. The only things 

 in common between the ovens were the fire-room and the chimney. 

 The ash-pits were the entire width of the grate, and the distance 

 from the under side of the grate-bars to the bottom of the ash-pit 

 was nearly five feet. This permitted a double current of air to. 

 form in the ash-pit, the cold one entering at the front near the 

 bottom, passing toward the back end, becoming gradually warmed 

 by the intense heat from the grate, a part entering the oven 

 through the grate, and the rest finally passing out of the ash-pit 

 at the front at a temperature of 300. By closing the furnace so 

 as to prevent the return current, the temperature of the ash-pit 

 could be raised to 500. The success of these furnaces worked 

 an immediate change in the whole tannery economy. Hitherto 

 tanneries had been limited to the banks of streams, where they 

 could get good water-power. Now such power was not necessary. 

 Tanneries could be located in the open flats, where access was 

 easy, and where the inconveniences and expenses of elevations 

 could be avoided. Fuel was no longer an item of importance. 

 Tanners, therefore, were not obliged to confine themselves to one 

 great building, but they could spread out into as many smaller 

 ones as their convenience and business demanded. They, further- 

 more, were no longer obliged to consider the cost of generating 

 steam, and as a result labor-saving machinery commended itself 

 to all. The discovery of this method of burning wet spent tan 

 has been the determining element in the construction of the 

 modern tannery. At the same time it has been one of the 

 most important factors in reducing the cost of the production 

 of leather. 



From the definition of leather already given a chemical or 



TOL. XLI. 27 



