SHARP. 
iedg^nent of the particular assistance, care, 
and industry of Mr. Abraham Sharp ; 
■whom, in the month of August 1688, he 
brought into the observatory as his amanu- 
ensis ; and being, as Mr. Flamsteed tells 
us, not only a very skilful mathematician, 
but exceedingly expert in mechanical ope- 
rations, he was principally employed in the 
constructioh of the mural arc ; which in the 
compass of fourteen months he finished, so 
greatly to the satisfaction of Mr. Flamsteed, 
that he speaks of him in the highest terms 
of praise. 
“This celebrated instrument, of which 
be also gives the figure at the end of the 
Prolegomena, was of the radius of 6 feet, 
yr inches ; and, in like manner as the sextant 
was furnished both with screws and diago- 
nal divisions, all which were made by the ac- 
curate hand of Mr. Sharp. But yet, whoever 
compares the different parts of the table 
for conversion of the revolutions, and parts 
of the screw belonging to the mural arc, 
into degrees, minutes, and seconds, with 
each other, at the same distance from the 
zenith on different sides ; and with their 
halves, quarters, &c. will find as notable a 
disagreement of the screw-work from the 
hand divisions, as had appeared before in the 
work of Mr. Tompion : and hence we may 
conclude, that the method of Dr. Hook, 
being executed by two such masterly hands 
as Tompion and Sharp, and found defec- 
tive, is in reality not to be depended upon 
in nice matters, 
“ From the account of Mr. Flamsteed it 
appears also, that Mr. Sharp obtained the 
zenith point of the instrument, or line of 
collimation by observation, of the zenith 
stars, with the face of the instrument on 
the east and on the west side of the wall ; 
and that having made the index stronger 
(to prevent flexure) than that of the sex- 
tant, and thereby heavier, he contrived, by 
means of pulleys and balancing weights, to 
relieve the hand that was to move it from a 
great part of its gravity. Mr. Sharp conti- 
nued in strict correspondence with Mr. 
Flamsteed as long as he lived, as appeared 
by letters of Mr. Flamsteed’s, found after 
Mr. Sharp’s death, many of which I have 
seen. 
“ I have been the more particular in what 
relates to Mr. Sharp, in the business of con- 
structing this mural arc, not only because 
we may suppose it the first good and valid 
instrument of the kind, but because I look 
upon Mr. Sharp to have been the first per- 
son that cut accurate and delicate divisions 
VOL. VI. 
upon astronomical instruments, of which, 
independently of IMr. Flamsteed’s testimony, 
there still remain considerable proofs ; for, 
after leaving Mr. Flamsteed, and quitting 
the department above mentioned, he retired 
into Yorkshire, to the village of Little Hor- 
ton, near Bradford, where he ended his days 
about the year 1743 (should be in 1742), and 
where I have seen not only a large and very 
fine collection of mechanical tools, the prin- 
cipal ones being made with his own hands, 
but also a great variety of scales and instru- 
ments made with them, both in wood and 
brass, the divisions of which were so exqui- 
site, as would not discredit the first artist of 
the present times ; and I believe there is 
now remaining a quadrant, of four or five 
feet radius, framed of wood, but the limb 
covered with a brass plate, the subdivisions 
being done by diagonals, the lines of which 
are as finely cut as those upon the quad- 
rants at Greenwich. The delicacy of Mr. 
Sharp’s hand will indeed permanently ap- 
pear from the copper-plate, in a quarto 
book, published in the year 1718, intituled 
‘ Geometry Improved, by A. Sharp, Plii- 
lomath,’ (or rather 1717, by A. S. Philo- 
math) whereof not only the geometrical 
lines upon the plates, but the whole of the 
engraving of letters and figures were done 
by himself, as I was told by a person in the 
mathematical line, who very frequently at- 
tended Mr. Sharp in the latter part of his 
life. I therefore look upon Mr. Sharp 
as the first person that brought the affair 
of hand division to any degree of perfec- 
tion.” 
Mr. Sharp kept up a correspondence by 
letters with most of' the eminent mathema- 
ticians and astronomers of his time, as 
Mr. Flamsteed, Sir Isaac Newton, Dr. 
Halley, Dr. Wallis, Mr. Hodgson, Mr. 
Sherwin, &c. the answers to which letters 
are all written upon the backs or empty 
spaces of the letters he received, in a 
short hand of his own contrivance. From 
a great variety of letters (of which a lafge 
chest-full remains with his friends); from' 
these and many other well known facts it is 
evident that Mr. Sharp spared neither pains 
nor time to promote real science. Indeed, 
being one of the most accurate and indefa- 
tigable computers that ever existed, he 
was for many years the common resource 
for Mr. Flamsteed, Sir Jonas Moore, Dr. 
Halley, and others, in all sorts of trouble- 
some fmd delicate calculations. 
Mr. Sharp continued all his life a bache- 
lor, and spent his time as recluse as a her- 
G 
