509 



IV. " On the General Forms of the Symmetrical Properties of 

 Plane Triangles." By THOMAS DOBSON, Esq., B.A., Head 

 Master of the School-Frigate ' Conway/ Liverpool. Com- 

 municated by Capt. E. A. INGLEFIELD. Received Decem- 

 ber 3, 1861. 



(Abstract.) 



The symmetrical properties of plane triangles have been fully ex- 

 pounded in a series of six papers dated 1835, 1836, 1842, 1843, 

 1845, and 1848 respectively, in the 'Lady's and Gentleman's Diary,' 

 published annually by the Stationers' Company of London. Either 

 from being the work of different hands, or from the earlier papers 

 having been written before the importance of symmetry in mathe- 

 matical formulae was duly appreciated, the series of papers leaves 

 much to be desired as to uniformity of method. 



By assuming the usual expressions for the area of a triangle, as 

 in the present paper, with a few other expressions of an equally ele- 

 mentary nature, all the well-known symmetrical properties of plane 

 triangles may be readily deduced, by a little skill in the combination 

 of algebraical symbols, without leaving the plane of the triangle, 



But the author has preferred to use a method which is at once 

 general, simple, and uniform. This consists in referring the sym- 

 metrical points connected with a triangle to an indefinite plane, and 

 establishing by an elementary process certain general formulae, each 

 of which can be made to yield several cognate plane properties when 

 different definite positions are assigned to the plane of reference. 



V. " Note on Ethylene-Dichloride of Platinum." By P. GRIESS, 

 Esq., and C. A. MARTINS, Ph.D. Communicated by Dr. 

 HOFMANN. Received December 16, 1861. 



About thirty years ago, Zeise obtained, by the action of dichloride 

 of platinum upon alcohol, a compound which he found to have the 

 following composition, 



C 2 H 4 Pt 2 Cl, 



This formula was corroborated by the analysis of a series of com- 

 pounds which this body forms with the chlorides of some of the 



VOL. XI. 2 O 



