LEA THER-MAKING. 



349 



favorite one with tanners on this side of the water. Again, the 

 process of depilation is still further hastened by the use of a 

 mineral acid, like sulphuric, or by the handling of the hides in 

 the old sour liquors where the tannic acid has become largely 

 converted into gallic acid. There are strong advocates of both 

 cold sweating and warm sweating, and of acid and non-acid 

 methods, but there are no data on which pre-eminence can be 

 assigned to any one of them. All have played an important 

 part in abbreviating the tanner's work. Following depilation 

 the hides are colored or passed through a series of vats contain- 

 ing liquors of varying strengths, and then laid away. Here, also, 

 it is a matter of opinion as to what is the proper time that 

 should be given to each of these operations. The late Hon. 

 Gideon Lee, in a course of lectures on the art of tanning, de- 

 clared, that he found quick-tanned leather of firmer and closer 

 texture, and at the same time heavier and more durable. By 

 keeping the hides too long in the liquors or vats the gelatin 

 was disolved. But, whatever the general census of opinion, these 

 processes have reduced the time required in the tanning of a hide 

 from twelve and eighteen months to four and six months. Visions 

 of a still greater abbreviation have been common, and " quick tan- 

 ning processes" appear about so often. Some of these are his- 

 torical. They include attempts to force the tannin into the hide by 



Fig. '.i. Belt Splitting Machine. 



hydrostatic pressure, and by the pressure of the air under an ex- 

 hausted receiver. They include the application of the principles 

 of osmose and kyanizing. The latter experiment was made by a 

 young English engineer, who in his early life had been engaged 

 in preserving wood by kyanizing with chemical agents. He came 

 to this country and spent ten thousand dollars in constructing a 

 large iron, egg-shaped, copper-lined tank. This was capable of 

 holding one hundred butts, and of resisting an immense pressure. 

 He provided pumps so that he could exhaust the air of this tank, 



