January 22nd, ipoi.] PROCEEDINGS. xi 



in the room. The danger from the use of such tapers might not 

 be great, but opinions as to the effect of continued small doses 

 of arsenic have lately been profoundly modified. 



The tapers were shewn and the presence of arsenic in them 

 demonstrated, a piece not more than an inch long sufficing 

 to give marked characteristic reactions. 



Dr. C. H. Lees mentioned a very compact formula for the 

 circumference of an ellipse, viz. : — 



3 2 



perimeter = 27 



where a and b are the semi-axes of the ellipse. Dr. Lees stated 

 that he had found the error of this formula to be as follows : — 

 when d='4.a less than 'i per cent. 



the formula giving a result less than the true perimeter in each 

 case. The formula, which was established in a communication 

 to the Messenger of Alathematics in Feb. 1883, by Mr. Thomas 

 Muir, is readily calculated with the aid of Barlow's tables. 



