Graduation of Afrommlcal Injlmments. 25 
that of the firmeft kind ; there being fcarcely need of magnify" 
ing glaffes in any part of the operation. 
In the year 1 748 I came to fettle in London ; and the fir ft 
employment I met with was that of making philofophical in- 
liniments and apparatus. In this fituation, my friend Hindley, 
from a principle the reverfe of jealoufy, fully communicated to 
me, by letter, his method of divifion ; and though I was enjoined 
fecrecy refpedting others (for the reafons already mentioned), 
yet the communication was exprefsly made with an intention 
that I might apply it to my own purpofes. 
The following are extracts from two letters* which contain 
the whole of what related to this fubjefl ; and fince I have many 
things to obferve thereon, fo that the paraphrafe would be much 
greater than the text, I think it befl: not to interrupt the defcrip- 
tion with any commentary, as perhaps his own mode of ex- 
preffion will more briefly and happily convey the general idea 
of the work than any I can ufe inftead of it. 
My dear Friend, York, 14 Nov. 1748. 
AS to what you was mentioning about my brother’s knowing 
how I divided my engine plate, I will defcribe it as well as I 
can myfelf ; but you will want a good many things to go 
through with it. 
The manner is this : firft chufe the largeft number you want, 
and then chufe a long plate of thin brafs ; mine was about one 
inch in breadth, and eight feet in length, which I bent like an 
hoop for an hoglhead, and foldered the ends together ; and 
turned it of equal thicknefs, upon a block of fmooth-grained 
wood, upon my great lathe in the air (that is, upon the end of 
the mandrel) : one fide of the hoop muft be rather wider than 
Vol.LXXVI. E the 
