Processes in the Use/id Arts. 343 



now used, which fixes in the cutter-frame d d, by the screws v, v, which 

 have conical holes in their ends at d, to receive the ends t, t, of the axis of 

 the cutter, and large round heads, with milled edges, similar to those pro- 

 posed for the sciev)sf,f, the screws v, v, are fixed tight by others, w, w, y 

 is a brass virrel, round which the line passes from the cutter, and communi- 

 cates the motion, x is the cutter, which is a circular piece of steel fixed on 

 the axis with its surface perpendicular to the length of the axis, and around 

 its edge are sharp teeth for cutting the teeth of the wheel. 



Suppose now, that the second frame, with its attached pentagraph, as 

 before described, is fixed to the cutting machine, and instead of the wheel 

 to be cut being fixed on the top of the mandrill at p, let a piece of steel be 

 placed there, and by the action of the pentagraph, as before described, let 

 this steel be cut into the shape of the required part of the epicycloidal 

 curve wanted for the teeth of the wheel, — this piece of steel, when proper- 

 ly shaped otherwise, may then be fixed on the axis t, t, and, with the cut- 

 ting-frame as now used, may be employed as the cutter for the wheels, and 

 their teeth will still have the required form ; the dotted lines at z, show 

 the shape which this cutter would have, instead of its presenting a thin 

 edge as at x. 



The difficulty in this method, appears to me to lie in making teeth to 

 this cutter, so as not to injure the true form of the curve, — an ingenious 

 mechanic may find himself capable of overcoming this. Perhaps, after the 

 teeth have been cut by the method I first proposed, an instrument, of the 

 form of the dotted lines at z, with its curves highly polished, may, with 

 advantage, be used as a burnisher, to prevent the injuring the true form of 

 the teeth, by finishing them up by any other method. 



I am, Sir, 



Your obedient Servant, 



To Dr Brewster. Peter Lecount, 



Midshipman Royal Navy. 



2. Description of a Single Weather Sluice, invented by Robert Thou, 

 Esq. Rothesay, Plate VI. Fig. 9. 



One of the purposes to which this apparatus is applicable, is to regulate 

 the supply of water between a reservoir and mill, or other works, where 

 the former is at a great distance from and high above the latter ; where 

 several streams fall into the aqueduct between them, and where the 

 adoption of apparatus, Vol. III. Plate I. Fig. 9, might be considered too 

 expensive. But it may also be applied to several other purposes, as will 

 readily occur to such as may have occasion to adopt it. 



AB, part of an aqueduct, (close behind the tunnel of the reservoir,) in 

 which the water is always kept at the same level by an apparatus like that 

 of Vol. II- Plate IV. Fig. 5 or Fig. 6, placed upon the tunnel of the re- 

 servoir. The communication between this part of the aqueduct and that 

 below is opened or closed at pleasure by 



BC, a small sluice, (and several others of the same kind, which arc not 

 represented in the drawing,) that turns upon pivots at C. 



