Xig X19 Aro 
. ‘ ; X78 Xz10 
ML oe ety = | X79 Azo Agro | + Xsg , 
: X7,10 X9,10 
Xto Xs10 Xo,10 
Xis Xie Ario 
P gl Jr 
Xi3 X1,10 
== Za 7 7 
192 + + Ys¥o9 =| Xie Krio Xsio | + A36 ; 
> 
Xi1o X6,10 
Xi 10 X310 X60 
3 
2123 + + gly = X14 X17 X97 a. Xo4 5 
7 Xo, A4, 
by which the coordinates of the ninth point are expressed in the 
coordinates of the 8 other points of intersection. 
The obtained results for the products of the corresponding coor- 
dinates of the 9 points are forms of the 7224 degree. 
Observation: In quite the same way we can determine the 
eighth point common to three surfaces of the 2™¢ degree passing 
through 7 given points. We then obtain for the products of the 
corresponding coordinates of the 8 points expressions of the 56 degree. 
Physics. — J. C. SonaLkwijk: “Precise Isothermals V. The iso- 
thermal of hydrogen at 20°C. up to 60 atmospheres. (Com- 
munication N°. 70 (3¢ continuation) from the Physical Labo- 
ratory at Leiden, by Prof. H. KAMERLINGH ONNES). 
§ 1. The small number of observations made with hydrogen, of 
which the most important are those by Reanautt (Mém. de l'Ac. 
XXI) going up to 28 Atm. and those by AMAGAT, of which the 
published results begin only at 100 atm., together with the small 
