MATHEMATICAL DIYiDI^Q ENGINE. 



II. 



Improvements in a Mathematical Dividing Engine : by 

 Mr. J. Allan, of BlewiCs Buildings, Fetter Lane*. 



SIR, 



I 



beg leave to send to you, herewith, f(»v the inspection of Improvement 

 the Society of Arts &c., a model of my improvement on the J"cal 'dWidlr'** 

 mathematical dividing engine, which I have lately made, enjine. 

 containing that part which dift'ers in principle from those 

 made by the late Mr. Rninsden and others ; the drawings 

 or engravings of which are, I suppose, in the Society's pos- 

 session. I therefore am of opinion the Society will think, 

 that the wooden wheel I have sent, with the movable ring 

 on its edge, will be sufficient to demonstrate its good effect 

 in correcting the teeth or rack where the screw acts. You 

 will please to observe, that it is cut by a screw cutter, and 

 it is required to go many times round the engine before the 

 teeth are full. To effect this, I reversed the movable ring 

 not less than twenty times, so that I have not the least 

 doubt of the one ring having corrected the other to a degree 

 of perfection, which had not hitherto been obtained in 

 engines. 



This simple, easy, and correct way of making engines, 

 may be applied with great advantage to circular instruments, 

 for the purposes of astronomy and land surveying. If the 

 Society will do me the honour to appoint a Coromittse to 

 view the engine itself, I will demonstrate its effects. 

 1 am. Sir, 

 Your rery humble servant, 



JAMES ALLAN, 



Divider of Mathematical Instruments. 



^0, I«, BlewiCs Buildings, Fetter Lane, 

 iVor. 20, 1809. 



Mr. Allan's Description of his Mathematical Dividing 

 Engine, and his Method of forming it. 



My engine is of belmetal, thirty inches in diameter. I The engine 

 turned a brass ring abont three sixteenths of an inch thick, desctibed. 



♦ Trans, of the Soc. of Arts &c., vol XXVIII, p. 179. Th« gold 

 aaedal was voted to Mr. Allan for this improtement, 



and 



