( 484 ) 



llio (l(Mil)l(' (•(niii»()mi(l. All ;inal()<>()iis result was olilaiiied with the 

 methvl coiiiimmiikI. 



We iiia\ , therefdi-e, coine to the e(mcliisi(»ii that there exist no 

 e<)in|Mtu)Hls of salts oi' siilphoiiearhoxvlie acids with neutral siil|iliiirie 

 esters; there exist, iiowever, doiihle (Mmipouiuls of salts of the acid 

 esters of suljjhoiiearhoxvlie acids with salts of the acid sulphuric esters. 

 Tliis result ,<>ives rise to a Jiuiuiier of ipiestious some of which 

 Dr. Attkmv intends answering l»v practical experiments, liotli salts 

 are alkvl-metallic salts of dibasic acids whose acidic functions (at 

 all excnts in the case (»f metasulphohen/oic acid) lia\e a very 

 did'erent power, whilst sulphuric acid as oxysulphonic acid is some- 

 what c(uuparahle to isetlii(»uic acid which also exhibits the pro|)ei'ly. 



Mathematics. "<hi thi- sji/wrcs <>/ Monok A/'Av/y///// fo oni/'iKn-i/ 

 (!//(/ Idihii'ntKil pi'iicils of <j/i(f(/r<(f/r s/irj'tK't s." Ily I'roj. ,) an 

 i)K A'riks. 



1. In Part T of the "Proceedings of the Section of Sciences" 

 pa.ues 305 — 310, 1 have developed, makin.U' nse of FiKOi-Kit's cyclo- 

 uraphic i-epi-esentation, some properties with i-espect to the system 

 (d the ortlio|>lical circles of the coincs of a linear system. By 

 extendin«i' Imkhlkk's considei-ations to a four-dimensional space the 

 coi'respon(lin«i- case of the three-dimensional s|>ace mi<iht be ti-ealed. 

 In the follow in,u- essay the indicated extension on cpiadratic surfaces is 

 arrived at analytically. 



Giv(Mi /* the point of intersection of three mutually |>ei-pendicular 

 tauu-eni planes of the (piadratic sm-face ;S'' re[»resented by the e(juation 



These three tangent planes form with every fourth tangent plane 

 a tetrahedron circumscribe<l about S' that may be regarded as polar 

 tetrahedrou w ilh respect to the poiid-sphere (isotropic c<»ne) /' repre- 

 sented by 



So the invariant (t belonging to S- and /- is e(pial to zero'). 

 Therefore we have: 



1) See a.o. S.m.mu.nFif.i.i.eh, Anal. (u-om. <les Ranmes, 3d edilion, vol. I, p. 253, 

 where S^ is represented by an ellipsoid. 



