356 Mr. Walker on some Geometrical Principles [May, 



Sulphur 18-72 



Bismuth 80-98 



99-70 

 The artificial compound gave 



Sulphur 18-49 



Bismuth 81-51 



100-00 



Note. — In this abridgment of M. Rose's paper, I have not 

 given all his views of the atomic constitution of copper pyrites ; 

 for as he adopts the numbers of Berzelius in which the weight of 

 the atom of iron is double that generally admitted in this country, 

 the statements would be useless. He considers its probable 

 composition as one atom of sulphuret of copper with three atoms 

 of sulphuret of iron. It will, however, appear, that his analysis 

 of copper pyrites from Ramberg comes more nearly than mine to 

 what I have supposed to be the atomic constitution of this com- 

 pound ; namely, a compound of two atoms of protosulphuret of 

 iron and one atom of persulphuret of copper, or in 100 parts of 



Copper 34-78 



Iron y 30-44 



Sulphur 34-78 



100-00 

 (See Annals, N. S. vol. in. p. 301 .)—Edit. 



Article VII. 



A Memoir on some Geometrical Principles connected with the 

 Trisection of an Arc. By John Walker, Esq. formerly Fellow 

 of Trinity College, Dublin. (With a Plate.) 



(To the Editor of the Annals of Philosophy.) 



SIR, April 14, 1824. 



The following propositions I believe are new ; and, if I mis- 

 take not, they either extend, or promise to extend, the limits of 

 Plane Geometry. 



It has long seemed to me, that the moderns have too much 

 abandoned the attempt of trisecting an arc, by the right line and 

 circle. We know with what ardour the solution of that problem 

 was sought by the ancient mathematicians ; as well as how con- 

 siderably the science was advanced by their investigations, 



