2S 
Mr . Smeaton's Obfervattom on the 
DEAR FRIEND* 
York, 13 March, 1748-9. 
I THINK in your laft you feem to be apprehenfive of feme 
difficulties in drilling the hoop for dividing : Firft, that the 
center of the hole in the hoop might not be precifely in the center 
of the hole of the fteel chaps, it was drilled in ; but if I defcribed 
fully to you the method I ufed, I can fee no danger of error 
there : for my chaps were .very thick, and the two correfpond- 
ing holes were a little conical, and ground with a fteel pin ; 
firft one pair, and then the other, alternately, till the pin would 
go the fame depth into each. Then for drilling the hoop, I 
took any common drill that would pafs through, and bore the 
hole. After that I took a five-fided broach, which opened the 
hole in the brafs betwixt the fteel chaps, but would not touch 
the fteel ; fo confequently the center of the holes in the brafs 
muft be concentric with the holes in the chaps : and for altera- 
tions by air, heat, cold, &c. I was not above two or three hours 
in drilling a row of holes, as far as I remember. 
2dly, For drilling, in a right line, I had a thin brafs plate, 
faftened between the fteel chaps, for the edge of the hoop to 
bear againft, whilft I thruft it forward from hole to hole. 
What you propofe of an iron frame with a lead outfide, will be 
better than my wooden block ; but confidering the little time 
that paft, betwixt transferring the divifions of the hoop to the 
divifions of my dividing plate, I did not fuffer much that way. 
It was when I drilled the holes in my dividing plate that I ufed 
3 frame for drilling, which had one part of it that had a fteel 
hole, that in lying upon the plane of the dividing plate was 
fixed faft in its place for the point of the drill to pafs through 
then, at the length of the drill, there was another piece of 
3 
fteel* 
