THE RAMSDEN DIVIDING ENGINE, 731 



fendre). Tlie doctor's invention, which, like many of his inventions, has 

 proved to be of permanent and great utility in mechanics, consists of 

 an entire transmutation of the old stationary i)latform, with its mova- 

 ble appendages, into a movable platform inserted into a strong metallic 

 frame, with stationary and additional appendages ; the machine thus 

 converted into an engine or self-acting piece of mechanism consisted of 

 a strong frame ; the sliding supporting bars of the platform or plate 

 with a horizontal screw of adjustment for distance from the circular 

 file ; the dividing plate with a revolving arbor to receive the wheel to 

 be cut ; and the alidade fixed to the great frame in the position of a 

 tangent line to any of the dividing circles and applying its bent and 

 rounded point to the punched marks of division on the circle succes- 

 sively as the plate revolving in the act of cutting the successive teeth 

 of a wheel." 



In the year 1716, Henry Sully brought to England from France a 

 cutting engine, made by M. de la Faudriere, which has been mentioned 

 by Julien le Eoy and described by Tbioutin his " Traite d^Rorlogeric." 



In 1730, M. Taillemard made further improvements in the cutting 

 engine, particularly by introducing a tubed arbor instead of an arbor 

 with a square hole, which had been used before. 



After Taillemard, his apprentice Hulot continued toconstruct engines 

 in a superior way in France, and was succeeded by his son, whose exe- 

 cution was deemed equal to that of his father's. 



EARLY DIVIDING ENGINES. 



Smeaton, in a paper entitled " The graduation of astronomical in- 

 struments," read before the Eoyal Society at London, November 17, 

 1785, mentions an engine made in 1741, by Henry Hiudley, of York, 

 England, which indented the edge of any circle in such a way that 

 a screw with fifteen threads acting at once would, by means of a 

 micrometer, read off any given number of divisions, so as to answer 

 the purpose of subdividing the circle. 



It would appear that this engine was better adapted for cutting 

 toothed wheels for clock-work than for graduating circles with exact- 

 ness. 



The Due de Chaulnes, in a memoir to the Eoyal Academy of Science, 

 at Paris, published 1765, referred to the difficulties in obtaining perfec- 

 tion of the screw and notches of the rack " so that they be rendered 

 perfectly equal, notwithstanding the unequal density and hardness of 

 difierent portions of the metal so racked." He calls his method " the 

 explication of the new way of dividing." 



It is said that he constructed an engine which he claimed to be his 

 original invention, but unfortunately the want of " a perfect screw with 

 intervals exactly proportioned to the effective radius of his quadrant, 

 was a source of error that posterior contrivances were required to 

 remedy." 



