[ H9 ] 



XVIII. Communications from Mr. Allan avd Mr. Stan- 

 CLiFFE on Allan's Dividing Instrument. 



To Mr. Tilloch. 



Sir, i BEG leave to inform vou, that Mr. Standi (Te wrote 

 his first opinion of niy improvement on the maihemaiical 

 Dividing Engine, after he went home from seeing the 

 wooden model at the Society's house, ayid before lie saw 

 the engine itself. As I was surprised to see such an opinion 

 inserttd in the Society's Transactions, after giving his ap- 

 probation in so strong terms when before the Gentlemen of 

 the Committee of Mechanics appointed by the Society of 

 Arts to view the engine at my house on the 1 3th of De- 

 cember 1810, T n)entioned the circumstance to him, and 

 told him of some observations in a certain obscure pubUca- 

 lion ; in consequence of which he has thought proper to fa- 

 vour me with the enclosed paper, 



Mr. Stanclifle has for many years been justly celebrated 

 for his extraordinary nicety in dividing, as well as for 

 his extensive knowledge of the most useful instruments 

 in the mathematical line ; and any ideas that he commits 

 to paper on the subject of mechanism I consider to be 

 worthy of notice ; and I hope you are of the same opinion. 

 If so, I should be very happy to see it published in the next 

 Number of the Philosophical Magazine. 



I am, sir, with true respect, 



Your obedient servant, 



February 19, 181'2. JamES AlLAN. 



[COPY.j 

 To Mr. Jllan. 

 Sir, — I HAVE lately seen in the Retrospect (No. 30) 

 of philosophical, mechanical, Sec. discoveries, some very 

 strange remarks in the observations on the improvement on 

 the Dividing Engine made by you, which I am clearly of 

 opinion must have had their foundation in prejudice or ex- 

 treme ignorance, or perhaps both. Here \ shall not enter 

 into any detad or vindication of what I said respecting xxxy 

 opmion before the Gentlemen of the Society of Arts, of 

 the great perfection, I believed, and do still believe, that 

 may l)e produced irom your plan of racking or cutting the 

 teeth of a circle for the purpose of dividing mathematical 

 instruments. However, by way of explanation, I will 

 H 4 slightly 



