370 
Original it into a hoop, by pressing it upon the edge of a chock, 
Graduation. as directed by Hindley. ay 
“—y~=" — Farther than this, Smeaton’s paper cannot be consi- 
Ramsden’s 
method of 
dividing. 
dered as describing an original method of graduation, 
the remainder being directed to the ——s it into an 
engine, of which, in its proper place, we declined gi- 
ving a description, and here it would be inapplicable. 
We may however observe, that Smeaton has improved 
upon Hindley in every fy with his usual ingenuity 
and ability; and provided the foundation were good, so 
would be the superstructure. Smeaton was no advocate 
for large astronomical instruments, and therefore would 
have an engine constructed of sufficient magnitude to 
graduate any that ought to be made. 
Mr Smeaton’s paper was not well received by the 
instrument makers; but he predicted, that when half 
a century had worn off the prejudice against it, the 
method would be adopted and improved to the advan- 
tage of astronomy. But as Mr Troughton, in a paper 
to be noticed hereafter, ventures to make a quite con- 
trary prediction concerning it, and gives his reasons 
for it; we decline entering into the question. 
Considering the celebrity of Mr Ramsden, his long 
career and extensive practice in making instruments 
that required the nicest graduation, we have in this de- 
artment of our article comparatively little to say of 
ere Excepting the descriptions of his engines, we 
believe he never wrote upon the subject ; nor has ao 
one else, so far as we know, described how he proceed- 
ed. Troughton has indeed pointed out the manner in 
which he adjusted erroneous dots to their places; a 
practice which it is said was suggested to Ramsden by 
the adjustable waxed pieces of the Duc de Chaulnes. 
A pupil of Ramsden informs us, that in an early part 
of his practice he had used the scale of equal parts, 
agreeably to the manner of Bird, but that he soon 
abandoned it ; and that he had often varied his appa- 
ratus and method. At what time the method of coax- 
ing, as it is called, was first applied in the works of 
Ramsden, is perhaps known to no one except Mr 
Berge: this artist, who at his death sueceeded him, 
had long been his able and indefatigable assistant, and 
in the graduation of instruments had honoured the name 
of his employer, 
** By patient touches of unfvearied art.” 
That the coaxing could not have been in practice so 
early as the time when the dividing engine was made, 
may be inferred from the circumstance, that the de- 
scription of the engine was given in upon oath, and no- 
thing said about it. 
For many years previous to the publication of the 
following method by Troughton, the art of graduation 
had been carried on in secrecy and silence ; every ar- 
tist had, or pretended to have a method of his own, of 
which astronomers could only judge, perhaps indeed 
the best way, by the comparative exactness of the 
work that came from their hands. Mr Troughton’s 
paper was read to the Royal Society in February 1809, 
and appeared in the first part of the volume of the 
Phil. Trans, for that year.* It contains not only an‘ac- 
count of a methed invented by himself, and which he 
had successfully practised for many years, but also re- 
marks upon other methods, which had been, or were then 
in use. To abridge this work, after giving Bird’s at 
length, is what we will not attempt; for we think our 
readers may not be displeased to see Troughton’s ideas 
* The Royal Society voted to Mr Troughton the gold medal on Sir Godfrey Copley’s Donation, for his valuable Paper.— En. 
GRADUATION. 
upon the subject in general, expressed in his own way; _ Or 
we Gisretbes give e whole, notwithstanding a few bie: 
repetitions, that will thus be introduced into our ar- 
ticle. : : eh RE 
« It would ill become me, in addressing myself to 
the members of this Society upon a subject which | 
are so well enabled to appreciate, to arrogate to myself instr 
more than may be assigned as my due, for whatever of 
success may have been the result of my long continued 
endeavours, exerted in prosecuting towards i 
the dividing of instruments immediately subservient to the 
purposes of astronomy. A man very naturally will set 
a value upon a thing on which so much of his life has 
been expended ; and I shall readily, therefore, be par- 
doned for saying, that, considering some attainments 
which I have made on this subject as too valuable to be 
lost, and being enco , also, by the degree of at- 
tention which the Society has ever paid to prac- 
tical subjects, I feel myself ambitious of presenting - 
them to the public through what I deem the most re= 
spectable channel in the world. 
It was as early as the year 1775, being then ai hea 
tice to my brother, the late Mr John Troughton, that thor’s: 
the art of dividing had become interesting to me; the tion ea 
study of astronomy was also new and fascinating; and ™ 
I then formed the resolution, to aim at the nicer parts. 
of my profession. $09 
At the time alluded to, my brother, in the art of di- 
viding, was justly considered the rival of Ramsden; 
but he was then almost unknown beyond the narrow 
circle of the mathematical and optical instrument ma- 
kers, for whom he was chiefly occupied in the division, 
by hand, of small astronomical rants, and Hadley’s 
sextants of large radius. Notwithstanding my own em- 
ployment at that time was of a much ‘inferior nature, 
yet I closely inspected his work, and tried, at leisure Defee 
ours, on waste materials, to intitate it. With as steady theca 
a hand, and as good an eyé@, as young men generally Prt 
have, I was much disappointed at finding, that, after 
having made two points, neat and small, to my liking, 
I could not bisect the distance between them, without 
enlarging, displacing, or deforming them with the 
points of the eompasses. This circumstance gave me 
an early dislike to the tools then in use ; and occasion- 
ed me the more uneasiness, as I foresaw, that it was an 
evil which no practice, care, or habit, could. entirely 
cure ;—beam-compasses, spring-dividers, and a scale of 
equal parts, in short, appeared to me little better than 
so many sources of mischief. i 
I had already acquired a good share of dexterity as.a Tx 
general workman. Of the different branches of our suppo: 
art, that of turning alone seemed to me to border on be 
perfection. This juvenile conceit, fallacious as I after- 
wards found it, furnished the first train of thoughts 
which led to the method about to be described 5 for it 
occurred to me, that if I could; by any means, apply 
the principle of turning to the art of Side ae 
ments, the tools liable to objection a be dispensed 
with. The means of doing this were first suggested by 4ppii 
wheel ; the surface of the Earth presenting itself oe 
edge of the instrument to be divided, and the wheel of 
the perambulator. as a narrow roller aeting on that 
edge; and hence arose an idea, that some easy contri- 
vance might be devised, for marking off the revolutions 
and parts of’ the roller upon the instrument. | Since the 
year above-mentioned, several persons: have proposed to 
