Graduation of Afr Gnomical Injlrumenis . % 7 
would fit clofe on ; and by that means my right line was made 
into an equal divided circle of what number I pieafed. 
The engine plate was fixed on the face of the block, with a 
fteel hole fixed before it, to bore through ; and I had a point that 
would fall into the holes of the divided hoop ; fo by cutting 
fhorter, and turning the block lefs, I got all the numbers on 
my plate. 
I need not tell you, that you get as many prime numbers as 
you pleafe j nor that the diftance of the holes in the fteel chaps 
mu ft be-proportioned to the length of the hoop. 
You may afk my brother what he knows about my method 
of dividing ; but need not tell him what I have faid about it ; 
for I think neither he nor John Smith know fo much as I have 
told you^ though I believe they got fome knowledge of it in ge- 
neral terms — I defire you to keep the method of dividing 
to yourf elf and conclude with my beft wifhes, 
and am, dear Sir, yours, &c. 
Hen. Hindley. 
Though the above letter was in itfelf very clear and explicit, 
as to the general traces of the method, yet fome doubts occurring 
to me, a further explanation became neceffary. A copy of my 
letter not being preferved, the purport of it may be inferred from 
the anfwer, which was as follows : 
* The perfons here referred to were both bred with him. His brother, Mr. 
Roger Hindley, who has many years followed the ingenious profeffion of a watch- 
cap-maker in London, was fo much younger as to be an apprentice to him. Mr. 
John Smith, now dead, had fome years paft the honour to work in the inllrument 
way, under the dire&ion of the late Dr. Demainbray, for his prefent Majesty. 
e 2 
DEAR 
