On Chemical Philosophy. 117 



wood, which would render it as light as a common square. The 

 blade may be very easily set to a right angle by making it coin- 

 cide with a line drawn on the arc for that purpose, where it may 

 be fixed by the clamp. 



Should any doubt arise as to the use of this improvement, I 

 shall be happy to attend a Committee of the Society, to explain 

 the difficulties that have given birth to it. 

 I am, sir. 



Your most obedient servant. 

 No. 11, Gee-street, Clarendon-square. Edmund TurRELL. 



To a Taylor, M.D. Sec. 



Reference to the Engraving of Mr . Turrell's T Square. 



Fig. 2, (Plate I.) shows a view of a T square with an adjust- 

 ing blade : consequently it can be set to any angle and fixed to 

 the arc G, by the thumb-screw D. 



Fig. 3, represents a section of fig. 2, in which the action of 

 the thumb-screw D, and the clamp E, may be more distinctly 

 seen, as likewise the screw F, upon which the blade turns as a 

 centre. 



The screw F being withdrawn, permits the blade to be taken 

 out, and the edges repaired, if they should receive any injury from 

 wear or accident. The arc G, being divided into degrees, per- 

 mits the blade to be placed at any angle where it may be fixed 

 by the thumb-screw D. 



XX. On Chemical Philosophy . By A/r. Matthew Allen *. 



Appendix to Essay I. 



L HE reason why I have included the views noticed in Essay I. 

 under the title Chemical Philosophy, is not alone that the 

 consideration of electricity, galvanism, caloric, light, &c. are at 

 present more particularly investigated by the chemical philoso- 

 pher, but also because I believe the word chemistry had originally 

 the most extensive meaning. The ancients considered heat and 

 flame as the most prominent features in the operations of a 

 power, on which every motion, change, and phaenomenon de- 

 pended; and hence it received innumerable names, all expressive of 



• Mr. Allen's First Essay appeared in our number for Feb. last (vol. xlix. 

 p. 81 ), and we expected before this time to have laid the continuation be- 

 fore our readers. With the present communication we have received a 

 letter from the author, which gives but too distressing a reason (a family- 

 bereavement) for the delay in sending, the promised Essays — Essays which, 

 from the one already before the public, and that introduced in our present 

 Number, we have every rea.<!on to think, will not only amuse but afford so- 

 lid infiti-ttction. 



H 3 heat 



