saundb:rson. 
Dr. Saunderson was natiiially of a strong 
healthy constitution ; but being too seden- 
tary, and constantly confining himself to 
the house, he became a valetudinarian : and 
in the spring of the year 1739 he com- 
plained of a numbness in his limbs, which 
ended in a mortification in his foot, of 
which he died the 19tb of April that year, 
jn the 57th year of his age. 
There was scarcel}- any part of the ma- 
thematics on which Dr. Saiinderson had 
.not composed something for the use of his 
pupils. But he discovered no intention of 
publishing any thing, till, by the persuasion 
of his friends, he prepared his Elements of 
Algebra for the press ; which, after his 
death, were published by subscription in 
2 vols. 4to. 1740. 
He left many other writings, though none 
perhaps prepared for the press. Among 
these were some valuable comments on 
Newton’s Principia, which not only ex- 
plain the more difficult parts, but often 
improve upon the doctrines. These are 
published in Latin at the end of his post- 
humous Treatise on Fluxions, a valuable 
work, published in 8vo, 1756. His manu- 
script lectures too, on most parts of natural 
philosophy, might make a considerable vo- 
lume, and prove an acceptable present to 
the public if printed. 
Dr. Saunderson, as to his charactjei') was 
a man ot much wit and vivacity in conver- 
sation, and esteemed an excellent compa- 
nion. He was endued with a great regard 
to truth; and was such an enemy to dis- 
guise, that he thought it his duty to ^pcak bis 
thoughts at all times with unrestrained fr ee- 
dora. Hence his sentiments on men and 
opinions, his friendship or disregard, were 
expressed without reserve; a sincerity which 
raised him many enemies. 
A blind man, moying in the sphere of a 
matheniatician, seems a phenomenon diffi- 
cult to be accounted for, and has excited 
the admiration of every age in which it has 
appeared. Tully mentions it as a thing 
scarcely credible in his own master in phi- 
losophy, Diodotus ; that he exercised him- 
self in it with more assiduity after he be- 
came b)ind ; and, what he thought next to 
impossible to be done without sight, that he 
professed geometry, desgribing his diagrams 
go exactly to his scholars, that they could 
draw every line in its proper direption. St. 
Jerome relates a still more remarkable in- 
stance in Didymus of Alexandria, who, 
though blind from his infancy, and there- 
fore ignorant of the very letters, not only 
learned logic, but geometry also, to a very 
great perfection, which seems most of all 
to recpiire sight. But, if we consider that 
the ideas of extended quantity, which are 
the chief objects of mathematics, may as 
well be acquired by the sense of feeling as 
that of sight, that a fixed and steady atten- 
tion is the principal qualification for this 
study, and that the blind are, by neces.sity, 
more abstracted than others, (for which 
reason, it is said, that Democritus put out 
his eyes, that he might think more in- 
tensely), we shall perhaps find reason to 
suppose that there is no branch of science 
so much adapted to their circumstances. 
At first. Dr. Saunderson acquired most 
of his ideas by the sense of feeding; and 
this, as is commonly the case with the blind, 
he enjoyed in great perfection. Yet he 
could not, as some are said to have done, 
distinguish colours by that sense ; for, after 
having made repeated trials, he used to say, 
it was pretending to impossibilities. But 
he could with great nicety and exactness 
observe the smallest degree of roughness, or 
defect of polish, in a surface. Thus, in a set 
of Roman medals, he distinguished the ge- 
nuine from the false, though they had bc«i 
counterfeited with such exactness as to de- 
ceive a connoisseur who had judged from 
the eye. By the sense of feeling also, he 
distinguished the least variation; and he 
has been seen in a garden, whefi observa- 
tions have been making on the sun, to take 
notice of every cloud tliat interrupted the 
observation, almost as justly as they who 
could see it. He could also tell when any 
thing was held near his face, or when lie 
passed by a tree at no great distance, 
merely by the diflerent impulse of the air 
on his face. 
His ear was also equally exact. He could 
readily distinguish the 5th part of a note, 
By the quickness of this sense he could 
j udge of the size of a room, and of his distance 
fr om the wall. And if ever he walked over q 
pavement, in courts or piazzas which re- 
flected a sound, and was afterwards con. 
ducted thiUier again, he could' tell in what 
part of the walk he had stood merely by 
the note it sounded. 
Dr. Saunderson had a peculiar method of 
performi- g arithmetical calculations, by an 
ingenious machine and method which has 
been called his Palpable Arithmetic, and is 
particularly described in a piece prefixed 
to the first volume of his Algebra. That 
he was able to make long and intricate cal- 
culations, both arithmetical and aigebraicaj, 
