34 Mr. SmeAton’s Obfer nations on the 
but above all things the artift ftiould be himfelf cool ; that 
is, not in a ftate of fenfible perfpiration ; and there ftiould be a 
free circulation of air in the room. Things being thus condi- 
tioned in refpe£t to temperature* he may begin to drill 
the holes in one of the ftraps ; the pin being firft put 
through the chaps and through the fteel hole of the ftrap ; and 
the next hole, being drilled through the brafs with a common 
drill, that and every hole as it goes is to be finiftied with a taper 
broach, as prefcribed by Hindley ; and he may then prove or 
finiflbt every hole by the application of a thorough broach* 
made fo full as to require a degree of preffure to force it 
through ; and this broach being a little tempered, and the 
holes quite hard, there will be no fear of injuring the fteel 
holes 
Calling the hole in the fteel plates o, and obferving the 
time of beginning, you may proceed to drill 60 holes as pre- 
fcribed by Hindley ; and noting how long you have been 
about it, you may lay the work afide 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 
loft in a great degree -jr* After this paufe you may begin again, 
and go on to finifh 60 holes more; that is, to the length of 
The fteel holes in the chaps need not to be above one-twentieth of an inch in 
diameter ; and though it may be proper to make the fteel plate, of which they 
are formed, one-tenth of an inch thick, in order to give the fpring formed 
between them a convenient degree of ftiffnefs, yet they may be reduced (by cham- 
fering the outfides) to half that thicknels. 
f As there is not much, occalion for the artift to touch his work, the effe&s 
of that may alfo be very much avoided by wearing thick gloves; and the frkftion 
being but flight, and the work almoft continually in the vife, the variation of 
temperature in the metals concerned cannot be fenfible or conliderable. 
6 
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