OntheContadsofLmes and Surfaces of the Second Order. 119 



The analyses of the platinum salt, taken m conjunction with 

 *!, o of the base itself leave no doubt that the formula C^^ H W U 

 those of tl^.^;^^;^^^^^^^^^^^^ of the constitution of bebeerme, and 



"^i^S^^^^^^^ obtained by Maclagan and Tilley 

 f rlPi.Pnd on the imperfect pui-ification of the material em- 

 T Pd rtheii analY s^ The formula which they have given is 



" he time'they wrote. The more recent "-ef igf on^^^^^^^^^ 

 rent have given for that base the constitution 03" H^ IJ U , wtucli 

 has been coZned by the analyses of Mr. How m this labora- 

 ?nrv and though Maclagan and Tilley^s analyses approximate 



Hhistrmui:^^^^^^ the «rence IS too great to^^^^^^^ 

 bpiuff received as the expression of their results. Althou^n cei 

 Sly not Impossible, kwould have been very remarkable had 

 two bases so opposite m their properties really possessed the 



same constitution. 



XVII. An Enumeration of the Contacts of Lines ^^^d Svrfaces of 

 the Second Order. By J. J. Sylvestee, M.A., F.R.S. 



™S;' Z^L ,uafat,c toctjon .ay ^^ .«ted as the 



?i,£ given lines in the plane of the conic are represented by the 

 lamblelif of four letters, the locus is a surface of the second 

 ordei- b coordinates being the distances or multiples of the 

 distances of any point therein from four planes dra^Ti in the 

 f^acc in 1^^^ -face is contained, and so onforlociof four 



equation thereto. 



