ABRAHAM SHARP. 37^5 
their riglit ascension and polar distance, and tlie variations of the 
same while they change their loiigiltide hy one degree. 
Being’, however, of a weakly constitution, the fatigue of continually 
observing the stars at night, in a cold dense air, injured his health ; and 
for the recovery of it he returned to his house at Horton, where, as 
soon as he found himself in a state of convalescence, he fitted up an 
observatory of his own, having first made an elegant and curious 
engine for turning all kinds of work in wood or brass, and even irregular 
figu res, as ovals, wreathed pillars, &c. He constructed also most of 
the tools used hy joiners, clock-makers, oplicians, and mathematical 
instrument-makers. Tiie limbs or arcs of his large equatorial instru- 
ment, sextant, quadrant, &c, he graduated with the nicest accuracy, 
by diagonal divisions, into degrees and minutes. The telescopes he 
used were all of his own making, and the lenses were ground and 
adjusted with his own hands. 
At this time he assisted Mr. Flamsteed in calculating most of 
the tables in the second volume of his Kistoria Celestis, and made 
curious drawings of the constellations, which w'ere sent to Amsterdam 
to be engraved ; and though executed by a masterly hand, the origi- 
nals are said to have exceeded the engravings in beauty. In the year 
1689, Mr. Flamsteed completed his mural arc at Greenwich, and in 
the Prolegomena to Ins Historia Celestis, he acknowdedges, in a most 
ample manner, the valuable assistance he received from Mr. Sharp, 
whom in the mouth of August, 1688, he had brought into the obser- 
vatory as his amanuensis. As he was not only a skilful mathemati- 
cian, but expert in mechanical operations, he emjiloyed him chiefly 
in the construction of the mural arc, which, in tlie course of fourteen 
months, he finished so much to Mr. Flamsteed’s satisfaction, that 
he speaks of him in the highest terms of praise. 
The ingenious Mr. Smeaton, in a paper published in the Philoso- 
phical Transactions for the year 1786, says, that this mural arc may 
be considered as the first good and valid instrument of the kind, and 
that Mr. Sharp was the first person who cut accurate and delicate 
divisions upon astronomical instruments. The delicacy of Mr. Sharp’s 
hand will permanently appear from the copper plates of a quarto book, 
published in the year 1718, entitled, Geometry improved by A. Sharp; 
or rather, 1717, by A. S. Philomath, in which not only the geometri- 
cal lines on the plates, but the whole engraving of the letters and 
figures, were done by himself. At the same time this elaborate work 
affords an honourable proof of the author’s great abilities as a 
mathematician, and contains things well worth attention: 1. A large and 
accurate table of Segments of Circles, with the method of its construc- 
tion, and various uses in the solution of several difficult problems. 
2. A concise treatise of Polyedra, or solid bodies of many bases, both 
the regular ones and others ; to which are added twelve new ones, 
with various methods of forming them, and their exact dimensions in 
surds or species, and in numbers. The models of these polyedra he 
cut out in box-wood with astonishing neatness and accuracy. Few 
or none of the mathematical instrument-makers,, indeed, could exceed 
him in exactly graduating or neatly engraving any mathematical 
or astronomical instrument. In short, he possessed a remarkably 
