" iF 
__ Mr Ramsden, in his second effort to make an engine, 
ly successful, insomuch that a sextant di- 
vided by it, being subjected to: the examination of Bird, 
was by him reported to be fit for every purpose of nau- 
tical astronomy.” Ramsden’s account of this engine, was 
in 1777 published by the Board of Longitude, who re- 
Kia in uity with the sum of £300. Fora 
es £315, he — over tothe public the 
property e engine itself, on condition, that at sta- 
ices he should divide any instruments that might 
sent to him by other makers, so long as the. engine 
should be allowed to remain in his possession. 
__. Previous to the account of Ramsden’s being publish- 
. ed, and before its construction was generally known, 
<a Dollond made an engine; differing materially we 
lieve from the former ; but as it was never used ex- 
uation of instruments made by them, 
ent we can form of its quality, arises out 
ility of that well known house. 
. In the year 1778, the late MrJohn T ton comple- 
ted a uating engine, which at the full stretch of his 
means oceupied him for three years. In 
its general construction, this differs in no material re- 
from Ramsden’s, though it is generally, we be- 
lieve, thought to be superior in point of accuracy. The 
trade were so ill satisfied with Ramsden, on account of 
his keeping their work for an unreasonable length of 
time, as well as for the careless manner in which it was 
often divided by his assistants, that Troughton imme- 
diately, at augmented prices, found full employment 
for his ; and he has been heard to say, that by the care 
and industry of himself and his young brother, he soon 
. found himself as. well remunerated for making his en- 
gine, as Mr Ramsden had been by public rewards. 
s _ It was about 1788, that Mr John Stancliffe finished 
en- a dividing engine. This: accurate artist had been ap- 
1788. prentice to Headley of York, and for many years a fore- 
man to Ramsden, The latter derived much informa- 
tion from him in. the construction of his second engine, 
in which the cutting-frame of Hindley was adopted. 
In the first, the divisions were cut with the beam-com- 
, Which, compared with Hindley’s apparatus, is te- 
ne and inaccurate. Mr Stancliffe’s practice has al- 
| most exclusively been confined to making sextants, and 
their being held in the highest estimation, furnishes the 
most certain proof of the excellence of the engine by. 
which they were divided. 
It would be useless particularly to.enumerate all the 
j engines thathave been made for angular dividing ; per- 
haps there may be ten or twelve in London, generally 
copies of Ramsden’s second engine. The greatest novelty. 
that has appeared in this way, was given a few years ago 
by Mr James Allen, an industrious workman, which. he 
stiles a self-correcting method of racking the sat and 
{ which, with the usual ty of 
Arts, &c. was honow 
nature of, the 
with their goldmedal. Those 
i who wish to know more of it, may, by. consulting the 
journals ofthat Society, gain full information, and have 
an opportunity to examine whether or not it deserves 
its title. 
As in our article, we have not room for more than 
the description of one circular engine ;—as Ramsden’s 
i fas been copied into more than one work similar to our. 
; own ; and as that of the present Mr Troughton has not 
| ga the public eye, we give the'preference to the 
atter, which at our request he has lately communicated; 
i in the following letter.to Dr Brewster :. . 
y VOL. X, PART Je 
GRADUATION. 
353 
« Dear Sir, I remember that’ im a late conversation ——, 
between us, you gave me to understand, that a descrip- © jam 
tion of my circular dividing engine would be acceptable 
to you, in order to form a part of the article in your ‘be Editor, 
Encyclopedia to which it belongs. For that purpose, containing » 
I have at length drawn it up, not to my own satisfac~ description 
tion indeed, for I wished it to have been done well ; of “7 B- 
but such as it is I have the honour of presenting it to tn 
ou. “0 
The excellent engine of my late brother being fully. pine. com- 
four feet in diameter, gave to the operator, when at work pleted in 
near the centre, a position so painful, that it had done 1793- 
no ar to either his health or my own, and had mate- 
rially injured that of a worthy young man then my as- 
sistant; it was evident that, by ing one of stnaller 
dimensions, this evil would in a great measure be re« 
moved,.and I foresaw that by employing my own me- 
thod of original dividing from which to rack the plate; 
a considerable reduction might be effected without an 
sacrifice of accuracy. I also perceived, that by contri- 
ving the parts with more simplicity than Ramsden had 
done, I could get through the work at less than two- 
thirds of the labour and expence. 
Such were my motives for making an engine, and 
the work was accomplished in the year 1793. 
' ©The ray arts of this engine are represented by 
Fig. 1 a plan,and Fig. 2 an elevation, in PlateCCLX XIX. 
It is mounted upon a strong frame of wood, the upper 
part serving as a box to preserve it, and which at cer- 
tain places opens for use. This stand does not, like 
those of engines hitherto made, form a. part of the ma- 
chine ; it only serves to support it at a convenient. 
height, and is not, excepting the platform EE, at all re- 
resented in the Plate. The lowest of the engine 
isa heavy tripod of cast brass, nearly in the same state 
in which it came from the mould. Two of its branches 
are denoted at A, A, in the plan; the third is similar, 
but mostly covered by the work above. In Fig. 2. the 
tripod is also represented by AA, below which three 
finger-screws that support it upon the platform are seen, 
These screws, marked B in the elevation, serve the pur- 
pose of levelling the engine. They work in the tripod 
with their heads downwards, and are planted in the 
broad part where the two branches meet. At about two: 
inches from the centre of the tripod, and at equal distan- 
ces from each other, are fixed three conical tubes, ex- 
tending downwards —e three feet. Two of them ap- 
pear at C, C, the other is hidden behind the axis of the 
engine plate. They are connected at the lower ends 
by a strong piece of brass F, forming together with the 
centre of the i a frame wherein the axis revolves. 
The engine plate itself, represented by Gs in Figs, Fig & 
1, 2, and 5, was cast in one piece of brass, all except 
the circular limb. The form of the twelve radii respect- 
ing depth is seen in the elevation, and.a central part of 
four inches.diameter, equal in thickness to their greatest 
depth, connects them; but the broad circular centre- 
iece seen in the plan, as well as the circular ring shewn 
in the middle, are no thicker than the limb.. The limb, 
three inches broad and half an inch thick,.is formed 
without soldering ef one piece of fine plate brass; It 
is rabbetted upon the extremities of the radii, so as to 
bring its upper surface into the same plane with them, 
and there by rivets made permanently fast. 
The axis of the plate is. a strong conical tube D, four 
inches in diameter at the upper end, and half as much 
below. Its length is determined by the three cones of 
the tripod. At the. upper,end it is immoveably fixed to 
the centre of the plate ; the lower end terminates in 
an obtuse point of'steel. There is fastened in the up- 
2% 
PLATE 
CCLXXI®. 
Fig. 1. & 2. 
