The tension of the cloth is preserved by ratchet-wheels and catches to either roller, precisely as in a common tamLeuring tent ; and in order that it may be stretched laterally as well as vertically, at each side was a piece of iron filled with wire hooks, which took hold of the selvage of the cloth, and which operated exactly like those frames for drying cloth, used at bleachfields, and called by the name of stentevs. In the double framing at the right hand, that part of the machinery which forms the pattern is contained, and this consists of four wheels fixed upon the same axis, which was a bar of iron one inch square. Of these wheels, three were 18 inches in diameter, and one 26 inches. The wheel nearest to the front of the machine is a ratchet, and merely regulates the motion of the others. It was cus tomary to form two flowers by one revolution of the axis, because when the flowers were similar, every second row was reversed, and when dissimilar, every alternate row was of the same form. In the first case, the ratchet-wheel formed a flower by half a revolution ; in the second, the number of teeth corresponded to the number of loops or stitches in the respective flowers. The next wheel in order communicated the horizontal motion to the frame in which the cloth was suspended ; the third wheel gave the perpendicular motion ; and the lOurtIn or '26 inch wheel, gave a rotatory motion to the needles upon their own axes. The second and third of course, were those immediately employed in the formation of patterns ; and it may be proper in this place to give sonic account of the principle by which they were fitted for this purpose, as it is by far the most curious and least understood part of the whole ma chinery.
The principle upon which this motion is constincted, and which is susceptible of infinite variety, depends upon the two following corollaries to the third law of motion, as given in Sir Isaac. Newton's Principia, and extract ed from Mr Motte's translation, edition 1803, pages 15, 16.
Cop. 1. A body by two forces conjoined N% ill describe the diagonal of a parallelogram in the same time that it would describe the sides of these forces apart.
" Cor. 2. And hence is explained the composition of any one direct force out of any two oblique forces ; and, on the contrary, the resolution of any one direct force into any two oblique forces; ii hich composition and resolution are abundant') confirmed from mechanics." Upon the application of this theorem, that profound and illustrious philosopher founded the first rational and satisfactory explanation of the causes of the elliptical orbits of the planets, and accounted for the causes by which the whole system of the universe is regulated ; and the recent discoveries of La Place, and other eminent philosophers of the French school, are merely extensions of the same general law, involv ing the effects produced by the gravitation of the planets towards each other, as well as towards the sun. 'Co apply this principle to the construction of the tambour machine, or any other requir ing extensively vat led motion, it was only necessary to produce two direct motions, which, as being the most simple and efficient mode of construction, \rove placed at right angles to each other, one being in a vertical, and the other in a horizontal direction ; and as it is easier to communicate motion to one body than to many, it was found better that the motions which produced a relative change of position between the cloth and the needles, so as to regulate the successive points of per foration, should be given to the former rather than to the latter. In the first construction of the machine, the
motion given to the cloth frame was effected by two screws, one placed vertically, and the other horizontally. As the machine in this state was wrought by the opera tor's hands and feet, and entirely under the guidance of his discretion, the screws were turned by his hands, by two small winches, so calculated, that when either winch was turned to the extent of a quarter or quadrant of one revolution, a shift of the cloth, equal to part of an inch, was produced. This was found a proper length when the motion was directly given by one screw. either vertically or horizontally. /Int when any intermediate angle was to be formed, it required that the shift should be less in both screws, as the oblique line produced by the combined action of both screws was always greater than either side apart, in the same ratio that the hypo thenusc of a right angled triangle exceeds that of either of the sides. When the screws were judiciously turned, this operation succeeded very well ; but as the ratio of the one to the other constantly varied, even the most care ful operators, totally ignorant of the mo..t simple tart' principles of oigononu try, were in t onstant &lige r of error ; and «lien CliirlititCd to N101111 n or boys, which considerations of economy rend( red pc, desirabb , it was found impossible to place much reliance upon the quality and regularity of the work. These ri ason therefore, induced tic: inventor seriously to endeavour to find some remedy, which. by fixing the motions of the machine under regular mechanical laws, should entirely remove both the blunders and inaccuracies of human agency, an I this Le was enabled to effect by remov lug the se ens, and substituting the traverse wheels. When this point was gained, very little more NI. as necessary to render the machine entirely and this was speedily effected.
In order to form a rule by which a pair of wheels may be formed, to produce a straight line at any angle of obliquity, nothing more was necessary than to con struct a table of trigonometrical calculations from I° to 89° inclusive, the measure of the hypothenuse beila; always the side gisen =am% of an inch ; but to execute such minute measures with I ccuracy. it became neces sary to invent a machine for the regulation of those divisions. In order to effect this, he availed hinisc If partly of the principle of the common clock-make rs' cut ting engine, and partly of the best description which he could lied of llr Ramsden's celebrated fur dividing astronomical instruments. Combining these with such variations as suited his particular object. he contrived a cutting engine. by which lie was en•bh d to cut with considerable precision and accuracy to divisions so minute as the I20oth part of : n inch, and this was found quite competent for every practical purpose.