aU'Sotts of Hides and SUns. 1^ 



feparated from them by a paflage for a fniall cart or wheel- 

 barrow to fill the digefters occalionally with new tan, and to 

 remove it when fpent. The bottoms of the four front digeft- 

 ers, or thole neareft the vats, (liould be fome inches higher 

 tlian the edge of the vats, fo that, when the hquor is ready, 

 it may, by means of a (hoot, and turning the cock in the 

 digefter, run of itfelf into the vat where it is wanted. Over 

 each of thefe front digefters is to be placed a fecond, proje(il- 

 ing a little into it, fo that, by turning a cock, the liquor may 

 run from the upper into the lower digefter, without the trou- 

 ble of pumping; and over the fecond, a third placed in the 

 fame manner and for the fame purpofe. 



By this difpofition of the digefters all the labour of pump- 

 ing is avoided, except from each of the loweft to the upper- 

 ttioft one of the next row. The four inferior digefters muft 

 confequently be provided with an eye each, for the pump t© 

 ftand in when necefl'ary. 



Befides the cock or plug placed in the part of the fuperior 

 digefters which proje6ls into thofe immediately under them, 

 there muft be another in the fide for the purpofe of conveying 

 the liquor into the vats, when neceflarv, by means of a ftioot. 



As to the dimenfions of thefc veffels, their depth Ihould 

 not exceed two feet and a half, or three feet at moft ; but 

 they may be as wide as the breadth of the ftied or building, 

 where they are erected, will admit ; and, if large enough to 

 contain half a ton of bark at a time, the better will they 

 anfwer the defired end. They Ihould be made of wood, and 

 not pitched. Metallic or brick digefters would greatly mjure 

 the liquor; no cement, or mortar made of lime, fliould be 

 nfed in them, becaule lime dcftroys all the tanning principle 

 with which it comes in contadt. 



Though thefe obfervations are applicable chiefly where 

 new digefters of the moft convenient form are to be erefted, 

 yet even in old tan yards, where fome of the pits already in 

 ufc may be converted into digefters, their number and deptb 

 Hiould be attended to. There ftiould be twelve of them, at 

 leaft, if poflible, for the reafons already afligned ; that is, for 

 fupplying the neceflary quantity of liquor, and completely 

 cxhaufting the tan : their depth fhould not exceed three feet, 

 that the prclfure of too high a colunm of bark may not pre- 

 vent the water from diflulving all its parts equally, and that 

 the tan, by clodding, which it is apt to do, may not prevent 

 the liquor from running. No more water fhould be poured 

 on the lan than is futficient to cover it, and therefore the 

 eyes of thefe fpenders fliould be no larger than is ablblutcly 

 i^ocefl'ary for the pump to ftand iu. 



It 



