^01 Maiiujailun if Htils, 



is dipped in, and immediately again taken out and fqueezed bended and rolled, by prefTure 

 in different dirc^lions, fomeiinies with the hand defended by leather, and fometimes by 

 means of a roller or other fimilar iiiftrument. The Inimerfion and working of the felt is 

 repeated, and the operation continued until the ftuff is well condenfed, and has acquired 

 the requifiie folidity. 



Such are the proceffes ufed in manufaflorics, and they conftitute the whole of what is 

 explained in the Defniftkn des Arts, and in the new edition of the Encyclopedie Mtthodiquc. 



Since the operation of fulling is employed to form a denfe and conipa£t ftuff with the 

 fibres or hairs, and to determine the intimate cohefion of its component parts; and fincc 

 the mere mechanical operation is not fufficient for this purpofe, even with the affiftance of a 

 vater-bath at the boiling-heat, without the addition of the lees as a neceffary condition ; — 

 this laft muft be conlldered as a chemical folvent, which ads direcflly on the fubftancc of the 

 hairs themfelves, and produces, either by foftening or fwelling them, an alteration neceffary 

 to infure the cohefion of the different fibres of the ftuff. But the lees being compofed of 

 the mucilaginous and colouring parts which are feparated, together with a great quantity of 

 tartar, or the acidulous tartrite of pot-a'fti, it became neceffary to afcertain, in a pofitive 

 manner, what might be the principle of its action. 



The editor of the Encyclopedic has not hefitated to affirm, that it is the alkali or pot-a(h 

 of the lees which determines the fulling. But in order to fliew how erroneous this affertion 

 is, nothing more is neceffary than to dip a piece of blue paper into the bath, by which the 

 former becomes inftantly red ; and if, after feveral hours work, the ftate of tlie bath be 

 again examined, it is found that the acidulous tartrite of pot-afti is partly exhaufted, and 

 the workmen foon perceive, from the difficulty of continuing their work, that a new quan- 

 tity is required to be added. And again, if we confider the fparing folubility of the acidulous 

 tartrite of pot-afli in cold water, it is eafily feen why in this procefs the water mult be kept 

 nearly boiling. Whence it is evident that it muft adl by the portion of acidule it contains. 



This firft obfervation induced me to think that the fulphuric acid might be advantageoufly 

 fubftituted in the place of the lees ; and as twelve pounds of lees are ufually added to one 

 hundred of water, I eftimated by approximation that one gros of fulphuric acid would be 

 equivalent to at leaft one pound of the lees, and confequently that twelve gros of fulphuric 

 acid would be fufficient for one hundred pounds of water. 



Experiment foon confirmed my conjeflures ; and after a firft trial, which the manufac- 

 turer did not confent to make without trepidation, it was afcertained that the ufe of the 

 fulphuric ;icid is greatly to be preferred to that of wine-lees; that it is not only much more 

 economical, but ftill more convenient in the ufe ; and, what is ftill more important, the 

 health of the workman is not injured by the excefs and duration of the heat, the thick va- 

 pours, and the difgufting odour which exhales from the bath, particularly when the lees 

 have been altered by mouldinefs and putrefailion, which is very common in thefc manu- 

 faftories *. 



"* I cannot avoid mentioning a fmall inconvenience which was experienced the firft time the fulphuric acid 

 was ufcd. A bottle was filled with the quantity requifitc for the bath intended to be made ufe of; and as the 

 acid was poured out from feme height without any precaution, fome drops were difperfcd, which, falling on 

 the hands or clothes of the operator, occafioned fpots by corrofion. To avoid this, it is only required that the 

 bcttic (houlJ be plunged in the Uith, and its contents poured out, fo as to occaGoD no fcattering of drops. C. 



la 



