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Ramsay, a particular person for the crime of which he himself 2160 teeth, in which an endless screw acts. Six revo- Ramsden's
Ramsden's stood convicted. In like manner, bad Mr Ramsay been lutions of the screw will move the wheel a space equal Machine.

a tyrant to his own slaves, though he might have argued to one degree.
against slavery in the abstract, on the broad basis of vir Now a circle of brass being fixed on the screw arbor,
tue and religion, he never could have arraigned for si. having its circumference divided into 60 parts, each
milar cruelty a number of individuals in the very island division will consequently answer to a motion of the
which witnessed his own enormities.

wheel of 10 seconds, six of them will be equal to a mi-
But the melancholy part of the narrative is behind.

nute, &c.
The agitation given to his mind by these calumnies, “ Several different arbors of tempered steel are truly
and the fatigues be underwent in his endeavours to re ground into the socket in the centre of the wheel. The
scue from misery the most helpless portion of the human upper parts of the arbors that stand above the plane are
race, contributed to shorten a life in no common degree turned of various sizes, to suit the centres of different
useful. He had been for some time afflicted with a pain pieces of work to be divided.
in his stomach, for which he was prevailed upon, though “ When any instrument is to be divided, the centre
with great reluctance, to try the effects of air and ex of it is very exactly fitted on one of these arbors; and
ercise, by attempting a journey of 100 miles. But in the instrument is fixed down to the plane of the divid-
London, being seized with a violent vomiting of blood, ing wheel, by means of screws, which fit into holes
he was unable either to proceed or to be removed home; made in the radii of the wheel for that purpose.
and in the house of Sir Charles Middleton he ended his “ The instrument being thus fitted on the plane of
days, on the 20th of July 1989, amidst the groans of the wheel, the frame which carries the dividing point
his family, and the tears of many friends.—Thus died a is connected at one end by finger-screws with the frame
man, of whom it is not too much to say, that “the bles which carries the endless screw; while the other end
sing of many that were ready to perish came upon him;" embraces that part of the steel arbor, which stands above
for whatever be the fate of the slave-trade (see SlA the instrument to be divided, by an angular notch in a
VERY), it is certain that his writings have contributed piece of hardened steel ; by this means both ends of
much to meliorate the treatment of slaves. He left be the frame are kept perfectly steady and free from any
bind him a widow and three daughters : and his works, shake.
besides those to which we have alluded, consist of a vo “ The frame carrying the dividing-point, or tracer,
lume of Sca-sermons, preached on board his majesty's is made to slide on the frame which carries the endless
ship the Prince of Wales, which show him to have been screw to any distance from the centre of the wheel, as
a master of true pulpit eloquence; and a Treatise on Sig- the radius of the instrument to be divided may require,
nals, which was certainly written, and we think printed, and may be there fastened by tightening two clamps ;
though we know not whether it was ever published. and the dividing-point or tracer being connected with

RAMSDEN's Machine for Dividing MATHEMA the clamps by the double-jointed frame, admits a free
TICAL INSTRUMENTS, is an invention by which these and easy motion towards or from the centre for cutting
divisions can be performed with exceeding great accu the divisions, without any lateral shake.
racy, such as would formerly have been deemed ivcre “ From what bas been said, it appears, that an in-
dible. On discovering the method of constructing this strument thus fitted on the dividing-wheel may

be mor-
machine, its inventor, Mr Ramsden of Piccadilly, re ed to any angle by the screw and divided circle on its
ceived 61 51. from the commissioners of longitude ; en arbor, and that this angle may be marked on the limb
gaging himself to instruct a certain number of persons, of the instrument with the greatest exactness by the di-
not exceeding ten, in the method of making and using viding-point or tracer, which can only move in a direct
this machine from the 28th October 1775 to 28th Oc line tending to the centre, and is altogether freed from
tober 1777: also binding himself to divide all octants those inconveniencies that attend cutting by means of a
and sextants by the same engine, at the rate of three sbil- straight edge. This method of drawing lines will also
lings for each octant, and six sbillings for each brass sex prevent any error that might arise from an expansion
tant, with Nonius's divisions to balf minutes, for as long or contraction of the metal during the time of divid-
time as the commissioners should think proper to let the ing.
engine remain in his possession. Of this sum of 6151. “ The screw-frame is fixed on the top of a conical
paid to Mr Ramsden, 300l. was given him as a reward pillar, which turns freely round its axis, and also moves
for the improvement made by him in discovering the freely towards or from the centre of the wheel, so that
engine, and the remaining 3151. for his giving up the the screw-frame may be entirely guided by the frame
property of it to the conmissioners, The following which connects it with the centre : by this means any
description of the engine, is that given upon oath by Mr excentricity of the wheel and arbor would not produce
Ramsden himself,

any error in the dividing ; and, by a particular contri-
“ This engine consists of a large wheel of bell-metal, vance (which will be described hereafter), the screw
supported on a mahogany stand, having three legs which when pressed against the teeth of the wheel always moves
are strongly connected together by braces, so as to make parallel to itself; so that a line joining the centre of the

Plate it perfectly steady. On each leg of the stand is placed arbor and the tracer continued, will always make equal cccclix. a conical friction pulley, whereon the dividing wheel angles with the screw.

Plata rests : to prevent the wheel from sliding off the friction Figure 1. represents a perspective view of the en- CCCCLX pulleys, the bell-metal centre under it turns in a socket gine. on the top of the stand.

“ Fig. 2. is a plan, of which fig. 3. represents a sec- Fig. 2. “ The circumference of the wheel is ratched or cut tion on the line na. (by a method which will be described hereafter) into “ The large wheel A is 45 inches in diameter, and

4 L 2


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fig. 3.

Fig. 3.

Ramsden's has ten radii, each being supported by edge-bars, as bered at every 6th division with 1, 2, &c. to 10. The Ramdea's
Machine. represented in fig. 3. These bars and radii are con motion of this wheel is shown by the index y on the machine

nected by the circular ring B, 24 inches in diameter screw-frame G.
and tlıree deep; and for greater strength, the whole is “ H represents a part of the stand, having a parallel i5,4$ 5
cast in one piece in bell-metal.

slit in the direction towards the centre of the wheel,
As the whole weight of the wheel A rests on its large enough to receive the upper part of the conical
ring B, the edge-bars are deepest where they join it; brass pillar P, which carries the screw and its frame :
and from thence their depth diminishes, both towards and as the resistance, when the wheel is moved by the
the centre and the circumference, as represented in endless screw, is against that side of the slit H which

is towards the left hand, that side of the slit is faced " The surface of the wheel A was worked very even with brass, and the pillar is pressed against it by a and flat, and its circumference turned true. The ring steel spring on the opposite side: by this means the C, of fine brass, was fitted very exactly on the circum- pillar is strongly supported laterally, and yet the screw ference of the wheel ; and was fastened thereon with may be easily pressed from or against the circumference screws, which, after being screwed as tight as possible, of the wheel, and the pillar will turn freely on its axis were well rivetted. The face of a large chuck being to take any direction given it by the frame L. turned very true and flat in the lathe, the fattened sur “ At each corner of the piece I are screws n of Fig. 4 face A of the wheel was fastened against it with hold- tempered steel, having polished conical points : two of fasts; and the two surfaces and circumferences of the them turn in conical holes in the screw frame pear o, ring C, a hole through the centre and the plane part and the points of the other two screws turn in holes round (b) it, and the lower edge of the ring B, were in the piece Q; the screws p are of steel, which being turned at the same time.

tightened, prevent the conical pointed screws from un“ D is a piece of hard bell-metal, having the hole, turning when the frame is moved, which receives the steel arbor d, made very straight L is a brass frame, which serves to connect the end- Fig. 1, 2, 6. and true. This bell-metal was turned very true on less screw, its frame, &c. with the centre of the wheel: an arbor ; and the face, which rests on the wheel at b, each arm of this frame is terminated by a steel screw, was turned very flat, so that the steel arbor d might that may be passed through any of the holes q in the Fig. 4 stand perpendicular to the plane of the wheel : this piece Q, as the thickness of work to be divided on bell metal was fastened to the wheel by six steel the wheel may require, and are fastened by the fingerscrews l.

puts r.

Fig. 1.&: " A brass socket Z is fastened on the centre of the “ At the other end of this frame is a flat piece of mahogany stand, and receives the lower part of the tempered steel b, wherein is an angular notch : when Fig. 6. bell-metal piece D, being made to touch the bell the endless screw is pressed against the teeth on the cir. metal in a narrow part near the mouth, to prevent any cumference of the wheel, which may be done by turoobliquity of the wheel from bending the arbor: good ing the finger-screw $, to press against the spring , Fig. 1. $ fitting is by no means necessary here; since any shake this notch embraces and presses against the steel arbor d. Fig. 2. in this socket will produce no bad eflect, as will appear This end of the frame may be raised or depressed by movhereafter when we describe the cutting frame.

ing the prismatic slide u, which may be fixed at any Fig. 1, 2, “ The wheel was then put on its stand, the lower height by the four steel screws v.

Fig. 1, 4, 6. edge of the ring B resting on the circumference of “ The bottom of this slide has a notch k, whose Fig. 1. & three conical friction-pulleys W, to facilitate its mo plane is parallel to the endless screw; and by the point tion round its centre. The axis of one of these pulleys of the arbor d resting in this notch, this end of the Fig. 3. is in a line joining the centre of the wheel and the frame is prevented from tilting. The screw S is premiddle of the endless screw, and the other two placed vented from unturning, by tightening the finger

so as to be at equal distances from each other. Fig. I. “ F is a block of wood strongly fastened to one of the “ The teeth on the circumference of the wheel were

legs of the stand ; the piece g is screwed to the upper cut by the following method :
side of the block, and bas half holes, in which the Having considered what number of teeth on the
transverse axis h turns: the half holes are kept toge circumference would be most convenient, which in this
ther by the screws i.

engine is 2160, or 360 multiplied by 6, I made two Fig. 1. & 4 “ The lower extremity of the conical pillar P termi screws of the same dimensions, of tempered steel, in

nates in a cylindrical steel-pin k, which passes through the manner bereafter described, the interval between and turns in the transverse axis h, and is confined by the threads being such as I knew by calculation a check and screw.

would come within the limits of what might be turned “ To the upper end of the conical pillar is fastened off the circumference of the wheel: one of the scre irs, Fig. 4.

the frame G, in which the endless screw turns: the which was intended for ratching or cutting the terth, pivots of the screw are formed in the manner of two was notched across the threads, so that the screw, when fru-tums of cones joined by a cylinder, as represented pressed against the edge of the wheel and turned round,

at X. These pivots are confined between half poles, cut in the manner of a saw. Then having a segment Fig. 5.

which press only on the conical parts, and do not touch of a circle a little greater than 60 degrees, of about the cylindric parts: the half holes are kept togetber by the same radius with the wheel, and the circumference screws a, which may be tightened at any time, to pre made true, from a very fine centre, I described an arch vent the screw from shaking in the frame.

near the edge, and set off the clord of 60 degrees on Fig. 1, 2,

“ On the screw-arbor is a small wheel of brass K, this arch. This segment was put in the place of the 4, 5. having its outside edge divided into 60 parts, and num wheel, the edge of it was ratched, and the number of 3


and 3.

nut w.

Fig. 1, 3

Fig. 4.

Fig. 4.

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amsden's revolutions and parts of tlie screw contained between coincide with the fixed wire; the screw was then care- Ramsden's dachine. the interval of the 60 degrees were counted. The fully pressed against the circumference of the wheel, by Machine.

radius was corrected in the proportion of 360 revolu- turning the finger-screw S; then, removing the clamp,
tions, which ought to have been in 60 degrees, to the I turned the screw by its handle nine revolutions, till
number actually found ; and the radius, so corrected, the intersection marked 240 came nearly to the wire ;
was taken in a pair of beam-compasses : while the then, unturning the finger-screw S, I released the screw
wheel was on the lathe, one foot of the compasses was from the wheel, and turned the wheel back till the in-
puc in the centre, and with the other a circle was de tersection marked 2 exactly coincided with the wire,
scribed on the ring; then half the depth of the threads and, by means of the clamp before mentioned, the di-
of the screw being taken in dividers, was set from this vision 10 on the circle being set to its index, the screw
circle outwards, and another circle was described cut was pressed against the edge of the wheel by the finger-
ting this point; a hollow was then turned on the edge screw S; the clamps were removed, and the screw turn-
of the wheel of the same curvature as that of the screw ed nine revolutions till the intersection marked i
at the bottoin of the threads : the bottom of this bol nearly coincided with the fixed wire ; the screw was
low was turned to the same radius or distance from the released from the wheel by unturning the finger-screw
centre of the wheel, as the outward of the two circles S, as before, the wheel was turned back till the inter-
before mentioned.

section 3 coincided with the fixed wire ; the divi1:5. 3. The wheel was now taken off the lathe ; and the sion 10 on the circle being set to its index, the screw

bell-metal piece D was screwed on as before directed, was pressed against the wheel as before, and the screw
which after this ought not to be removed.

was turned nine revolutions, till the intersection 2 “ From a very exact centre a circle was described nearly coincided with the fixed wire, and the screw . 1, 2, 3. on the ring C, about four-tenths of an inch within where was released; and I proceeded in this manner till the

the bottom of the teeth would come. This circle was teeth were marked round the whole circumference of
divided with the greatest exactness I was capable of, first the wheel. This was repeated three times round, to
into five parts, and each of these into three. These make the impression of the screw deeper. I then ratch-
parts were then bisected four times : (that is to say) ed the wheel round continually in the same direction
supposing the whole circumference of the wheel to con without ever disengaging the screw; 'and, in ratching
tain 2165 teeth, this being divided into five parts, each the wheel about 300 times round, the teeth were fi-
would contain 432 teeth ; which being divided into three nished.
parts, each of them would contain 144; and this space “Now it is evident, if the circumference of the wheel
bisected four times would give 72, 36, 18, and 9:

there was even one tooth or ten miuutes greater than the
fore each of the last divisions would contain nine teeth. screw would require, this error would in the first in-
But, as I was apprehensive some error might arise from stance be reduced to do part of a revolution, or two
quinquesection and trisection ; in order to examine the seconds and a half; and these errors or inequalities of

accuracy of the divisions, I described another circle on the teeth were equally distributed round the wheel at 7. the ring C, one tenth of an inch within the former, and the distance of nine teeth from each other. Now, as

divided it by continual bisections, as 2160, 1080, 540 the screw in ratching bad continually hold of several
270, 135, 67), and 33* ; and as the fixed wire (to be teeth at the same time, and, these constantly changing,
described presently) crossed both the circles, I could the above-mentioned inequalities soon corrected them-
examine their agreement at every 135 revolutions; (af- selves, and the teeth were reduced to a perfect equality.
ter ratching, could examine it at every 33}): but, not The piece of brass which carries the wire was now ta-
finding any sensible difference between the two sets of ken away, and the cutting screw was also removed,
divisions, 1, for ratching, made choice of the former; and a plain one (hereafter described) put in its place: .
and, as the coincidence of the fixed wire with an inter on one end of the screw is a small brass circle, having
section could be more exactly determined thao with a its edge divided into 60 equal parts, and numbered at
dot or division, I therefore made use of intersection in every sixth division, as before mentioned. On the other
both circles before described.

end of the screw is a ratchet-wheel C, having 60 teeth, 7.

“ The arms of the frame L were connected by a thin covered by the hollowed circle d, which carries two Fig. 5. piece of brass of three-fourths of an inch broad, having a clicks that catch upon the opposite sides of the ratchet hole in the middle of four-tenths of an inch in diameter; when the screw is to be moved forwards. The cylinacross this hole a silver wire was fixed exactly in a line der S turns on a strong steel arbor F, which passes to the centre of the wheel; the coincidence of this wire through and is firmly screwed to the piece Y: this with the intersections was examined by a lens seven piece, for greater firmness, is attached to the screwtenths of an inch focus, fixed in a tube which was at frame G by the braces v; a spiral groove or thread tached to one of the arms L (A). Now a bandle or is cut on the outside of the cylinder S, which serves winch being fixed on the end of the screw, the division both for holding the string, and also giving motion to marked on the end of the screw, the division marked 10 the lever J on its centre by means of a steel tooth n, on the circle K was set to its index, and, by means of that works between the threads of the spiral. To the a clamp and adjusting screw for that purpose, the inter- lever is attached a strong steel pin m, on which a section marked i on the circle C was set exactly to brasz socket r turns : this socket passes through a slit


Fig. 4,

(A) The intersections are marked for the sake of illustration, though properly invisible, because they lie under the brass plate.

Fig. 4.

Ramsden's in the piece p, and may be tightened in any part of half holes F and T, which were kept together by the Reusden's Machine. the slit by the finger-nut f: this piece serves to regu

screw Z.

Machin, late the number of revolutions of the screw for each “ H represents a screw of untempered steel, having Ramses tread of the treadle R.

a pivot I, which turns in the hole K. At the other Tig. 1.

“T is a brass box containing a spiral string; a strong end of the screw is a hollow centre, which receives the gut is fastened and turned three or four times round the bardened conical point of the steel pin M. When this circumference of this box, the gut then passes several point is sufficiently pressed against the screw, to pretimes round the cylinder S, and from thence down to vent its shaking, the steel pin may be fixed by tightenthe treadle R. Now, when the treadle is pressed down, ing the screws Y. the string pulls the cylinder S round its axis, and the “ N is a cylindric nut, moveable on the screw H; clicks catching bold of the teeth on the ratchet carry which, to prevent any shake, may be tightened by the the screw round with it, till, by the tooth n working in screws 0. This nut is connected with the saddle-piece the spiral groove, the lever J is brought near the wheel P by means of the intermediate universal joint w, d, and the cylinder stopped by the screw-head .z striking through which the arbor of the screw H passes. A front on the top of the lever J; at the same time the spring is view of this piece, with the section across the screw arwound up by the other end of the gut passing round the bor, is represented at X. This joint is connected with box T. Now, when the foot is taken off the treadle, the nut by means of two steel slips S, wbich turn on pins

the spring unbending itself pulls back the cylinder, the between the cheeks T on the nut N. The other ends Fig. 1. clicks leaving the ratchet and screw at rest till the piece of these slips S turn in like manner on pins a. One axis

t strikes on the end of the piece p: the number of revolu- of this joint turns in a hole in the cock b, which is tions of the screw at each tread is limited by the num fixed to the saddle-piece; and the other turns in a bole de ber of revolutions the cylinder is allowed to turn back made for that purpose in the same piece on which the before the stop strikes on the piece p.

cock b is fixed. By this means, when the screw is turn“ When the endless screw was moved round its axis ed round, the saddle-piece will slide uniformly along

with a considerable velocity, it would continue that mo the triangular bar A. Fig. 1.& 4. tion a little after the cylinder S was stopped: to pre “K is a small triangular bar of well-tempered steel,

vent this, the angular lever # was made ; that when the which slides in a groove on the saddle-piece P. The
lever J comes near to stop the screw x, it, by a small point of this bar or cutter is formed to the shape of the
chamfer, presses down the piece x of the angular lever; thread intended to be cut on the endless screw. When
this brings the other end of the same lever forwards, the cutter is set to take proper hold of the intended
and stops the endless screw by the steel pin je striking screw, it may be fixed by tightening the screw e, which
upon the top of it; the foot of the lever is raised again presses the two pieces of brass G upon it.
by a small spring pressing on the brace v.

“ Having measured the circumference of the dividingFig. 1, 2,6. “ D, two clamps, connected by the piece a, slide one wheel, I found it would require a screw about one ibread

on each arm of the frame. L, and may be fixed at plea- in a hundred coarser than the guide-screw H. The sure by the four finger-screws e, which press against steel wheels on the guide-screw arbor H, and that on the springs to avoid spoiling the arms : the piece q is made

ms: the piece q is made steel E, on which the screw was to be cut, were proto turn without shake between two conical pointed screws portioned to each other to produce that effect, by giving f, which are prevented from unturning by tightening the whieel L 198 teeth, and the wheel Q 200. These the finger-nuts N.

wheels communicated with each other by means of the Fig. 6. “ The piece M is made to turn on the piece q by intermediate wheel R, which also served to give the

the conical pointed screws f resting in the hollow cen threads on the two screws the same direction.
ters e.

s. The saddle-piece P is confined on the bar A by
“ As there is frequent occasion to cut divisions on in means of the pieces g, and may be made to slide with a
clined planes, for that purpose the piece y, in which the proper degree of tightness by the screws n." See Di.
tracer is fixed, bas a conical axis at each end, which VIDING INSTRUMENTS, SUPPLEMENT.
turns in half holes: when the tracer is set to any inclina For Ramsden'sequatorial or portable observatory, see
tion, it may be fixed there by tightening the steel screws B. Optics, No 89. and ASTRONOMY, N° 364. See also a
Description of the Engine by which the endless screw

long account of an equatorial instrument made by Mr of the Dividing Engine was cut.

Ramsden by the direction of Sir George Shuck burgh in

the Philosophical Transactions for 1793, art. x. p. 67. “ Fig. 9. represents this engine of its full dimensions In this instrument the circle of declinations is four feet seen from one side.

in diameter, and may be observed nearly to a second. “ Fig. 8. the upper side of the same as seen from The glass is placed between six pillars, which form the above.

axis of the machine, and turn round by two pivots plaA represents a triangular bar of steel, to which the ced on two blocks of stone. See also BAROMETER. triangular boles in the pieces B and C are accurately RAMSEY, a town of Huntingdonshire, 68 miles fitted, and may be fixed on any part of the bar by the north of London, and 12 north-east of Huntingdon.

It is situated as it were in an island, being everywhere “ E is a piece of steel whereon the screw is intended encompassed with fens, except on the west, where it is to be cut; which, after being hardened and tempered, separated from the terra firma by a causeway fortwo miles

. bas its pivots turned

in the form of two frustumg of cones, The neighbouring meers of Ramsey and Whitlesey, as represented in the drawing of the dividing engine which are formed by the river Nyne, abound with fish, (fig. 5.). These pivots were exactly fitted to the especially eel and large pikes. It was once famous for

screws D.

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