Uj^fiil Ncrices. — Ptiriftcathit tf PqI-AJIi in ike Large Way. 320 



3. Wheels tvUhoiit Crgs. 

 VERY much of the difpofal or tranfmiffion of mechanic force is effected by means of 

 wheels aftiug upon each other. The connexion of the moving parts is performed either 

 by the mutual aflion of teeth, or by ftraps, or by the friftion of one face of a wheel 

 againft another. I have feen a drawing of a fpinning-wheel for children, at a charity-fchoo!, 

 Ill which a large horizontal wheel with a (lip of buff leather glued on its upper furface, 

 near the outer edge, drove twelve fpindles at which the fame number of children fat. 'Hie 

 fpindles had each a fmall roller likewife faced with leather, and were c.ipable by an eafy and 

 inftantaneous motion of being thrown into contaifl with the large wheel at pleafure. Each 

 child could therefore throw her own part of the apparatus into work, or caufe it to fi:op, as 

 often or as long as (lie pleafed. The winding bobbins for yarn at the cotton-mills operate 

 on the fame fimple and elegant principle, which poflefTes the advantage of drawing the 

 thread with an equal velocity, whatever may be the quantity on the bobbin, and cannot break 

 it. 1 do not know that this principle has been applied in large M-ork, except in a faw-miU 

 by Mr. Taylor of Southampton. In this the wheels aft on each other by the contaft of 

 the end grain of wood inftead of cogs. It makes very little noife, and at the time it was 

 mentioned to me had been in wear about fourteen years. I fuppofe, of courfe, that there 

 is a contrivance for bearing the wheels firm againft each other by wedges at the fockets, 

 or rather by levers. 



IX. 



yf/; Eco?ioniical Procefs to obtain Pure Caujlic Alkali in ihe Large Way, iiiih Fufcd Pot-n/h, or the 

 Lapis Caujiku!, By Citizen BOUILLON Le GsANCJE *. 



X H E procefTesfor obtaining the cauflic alkali and fufed pot- alb, called lapis caufticus in 

 the difpenfatorics, being either defeftive or tedious, the Citizen Welter and myfelf have 

 endeavoured to abridge this operation, by ufmg a procefs which requires lefs time and ex- 

 pence, and is more certain and ufeful, particularly for obtaining the cauftic alkali in the 

 large way, which is fo neceflary in the arts and in chemical experiments. 



We believe, therefore, that praftical men will receive with pleafure the defcription of a 

 method by which no part of the pot-afli is loft, and which affords it in a ftate of purity, and 

 very cauftic, without much expence or apparatus. 



Our apparatus confifts of feveral veffels of white wood, or, which is better, calcareous 

 ftone, whofe dimenfions may be varied according to the quantities intended to be prepared. 

 'ITiofe which we have eftabliflied for the Polytechnic School are of ftone, of tlie internal 

 capacity of one foot cube, (fee Fig. 4, Plate XT V.) having their bottoms grooved by ■ 

 channels of an inch in depth and the fnme width, and fo far diftant from each other that 

 there are five or fix parallel, which terminate at an end in a fimilar groove, which croffes 

 the whole, and ferves as a gutter to colledl the falinc folution. In the middle of this laft an 



* Annales dc Chiniic, XXIf. 137. 



Vol. I. — October 1797. U u hole 



