VOL. LXXVI.] PHILOSOPHICAL TRANSACTIONS. '4Q 



for directing them always to that upright position, may be then adjusted and 

 fixed to the inside of the chap next the operator.* 



The performance of the ensuing part of this work should be at a season when 

 the temper of the air is not very variable; rather above the mean temper, sup- 

 pose at 60°, than below it; but above all things the artist should be himself 

 cool; that is, not in a state of sensible perspiration; and there should be a free 

 circulation in the room. Things being thus conditioned in respect to tempera- 

 ture, he may begin to drill the holes in one of the straps; the pin being first 

 put through the chaps and through the steel hole of the strap; and the next hole, 

 being drilled through the brass with a common drill, that and every hole as it 

 goes is to be finished with a taper broach, as prescribed by Hindley; and he may 

 then prove or finish every hole by the application of a thorough broach, made so 

 full as to require a degree of pressure to force it through ; and this broach being 

 a little tempered, and the holes quite hard, there will be no fear of injuring the 

 steel holes. Calling the hole in the steel plates o, and observing the time of 

 beginning, you may proceed to drill 60 holes as prescribed by Hindley; and 

 noting how long you have been about it, you may lay the work aside a length 

 of time, equal to the time you took in drilling; that any addition of warmth it 

 may have acquired in handling or working may be again lost in a great degree. 

 After this pause you may begin again, and go on to finish 60 holes more; that is, to 

 the length of 120 holes from the beginning; you then proceed in the same 

 manner with the other strap. 



Method of Drilling the hoop. — You are now prepared to commence the work 

 on the long or hoop-plate; and you proceed with it, in forming the first hole 

 with the chaps, as before directed by Hindley, and this first hole you call o. 

 You then place the straps one on each side the hoop, with their gaged edges 

 upward, and put the pin through the holes denominated 60 on the straps, and 

 through the first hole already made, and denominated O on the hoop; then, 

 bringing the gaged edges of the steel plates to be even with the upper or work- 

 ing side of the hoop, you pinch them together in the vise, and drill and broach 

 the hole through the st<?el plates, which will make the hole, number 60, on the 

 hoop. This done, you put the pin through the left-hand hole of the chaps, and 

 the hole marked o on the hoop-plate first made, and proceed to drill with the 



* It would be well, previous to the drilling of the steel chaps, that another hole was drilled in the 

 chaps, that should be somewhat above the upper edge of the straps, and in the middle between side 

 and side, to receive a steady pin in, before drilling the main holes ; for then a tempered steel pin, a 

 little taper, will; by driving it in as far as necessary, constantly answer this purpose from first to 

 last, so as to regulate the bodies in grinding, to be truly opposite : proper holes should also be drilled 

 for fixing the brass guide plate to one of the chaps. — Orig, 

 VOL. XVI. H 



