VOL. LXVIII.3 PHILOSOPHICAL TRANSACTIONS. 30Q 



the state of the weather, and other variable circumstances; these liquors are 

 also exceedingly apt to rot the leather, and, without great care, may injure it very 

 materially in its texture. \6. To obviate these inconveniences, you are to imitate 

 the bleachers of linen, who make use of a sour prepared by diluting the 

 strong spirit of vitriol (vulgarly, but improperly, termed oil of vitriol) with a 

 sufficient quantity of plain water. 



17. It was not without much difficulty that the bleachers could be prevailed 

 on to quit their old sourings, made either of rye or barley, or of sour butter- 

 milk, from a groundless fear, that the vitriolic soaring would corrode their cloth; 

 but the experience of many years has convinced them of their error, and now no 

 other souring is used. In like manner the tanners at first may some of them be 

 afraid to use the vitriol, but a little practice will show how far superior this sour- 

 ing is to what they have hitherto used. They will never find it subject to any 

 change in respect to strength from variations of weather, or diflTerent degrees of 

 heat ; and so far from tending to rot the leather, it gives unusual firmness ; and 

 the soles which are raised by the vitriolic souring are remarkably sound, and 

 always free from the slightest degree of rottenness. Besides, the same sour may 

 do for many parcels of leather, by adding a little vitriol to it ; and it need only 

 be thrown away, when it becomes too dirty for use, by the frequent succession 

 of hides. 



18. A wine pint of the strong spirit of vitriol, which will not cost more than 

 9 or 10 pence, is sufficient for 50 gallons of water, to prepare the souring at 

 first : therefore all you have to do, in raising the soles, is only to prepare them 

 before-hand in the usual way ; and, when they are fitted for the souring, mix up 

 a quantity of vitriol and water, according to the number of hides required to be 

 raised, still observing the proportion of a pint to 50 gallons, which will be 

 enough, if the vitriol be of the due degree of strength. The hides may lie in 

 the souring till you find them sufficiently raised, for they will be in no danger of 

 rotting, as they would be in the common corn sourings, which in time might 

 turn putrid, and rot the leather ; whereas the vitriolic souring keeps off putre- 

 faction. 



19. When the hides are sufficiently raised, put them directly into the ooze, 

 and go on with the tanning as in the old way ; and you will see that the lime- 

 water ooze penetrates raised leather even faster than it does buts or calf-skins, 

 allowance being made for their different degrees of thickness. 20. Let it be now 

 supposed that you have your cistern fixed, your lime-water prepared, and some 

 letches full of lime-water ooze, which has been run through 2 letches, in order 

 that the lime-water may completely spend its force on the bark ; you are not to 

 throw away what common ooze you have in stock in the yard, but only as it 



