Graduation of' Jljh onomical Injlrumenfs •• 3-7. 
operation carried on with fo much power, that any fmail ine« 
quality in the hardnefs. of the hrafs, or irregularity of furface 9 , 
cannot be fuppofed to affeft the place of the center of the hole 
nor will any fmail inequality that may be fufpe&ed from the. 
wear of the fteel holes fenfibly affedt the center of the hole, to 
which every thing is ultimately referred,. 
Method ^/’joining the Hoof ;* 
A more happy thought than that of Hindley’s, for joining? 
the two ends of the hoop, could fcarcely have been wiflied for^ 
in regard to preferving the fame equality of the fpace between; 
the holes contiguous to the joint, as in the other parts : for; 
though, geometrically fpeaking, the two fuddle plates, in which V 
the little cylindrical bolts are fixed, for bringing the terminating; 
holes of the hoop plate to their due distance, being one applied 
within the hoop,. and the other without, will belong to circles ; 
of different radii ; yet this difference being exceedingly fmail iff 
fuch thin metal, and fo great a radius, and one being as much? 
too. big for the hoop as the other is too little, when the bolts 
are put in, and the hoop in that part fet nearly to a circle by a" 
mould ; the mean between them affumed by the hoop, from 
the elaftic compreffiBility of the materials, will be the truth, . 
It mufti however, be remarked, that in the ufe of the ftraps* , 
the joining of the hoop fhould not be made at any part betwixt: 
an 1 19th and an 120th divifion, as fome inequality muft be 
fuppofed there, unlefs the^ faddle plates were adapted thereto 0 
The method the raoft eafily pradlifed, will be to continue the 
divifion upon the hoop, about twenty more than the completion 
of the number intended to form the circle^ and to cut off all the 
overplus ones at the beginning. 
The 
