( 658 ) 



of which one, lying within the Joop is closed. Within the loop 

 therefore, the surface shows an elevation of which the top almost 

 agrees with .v = 0.40, v = 0.06, j) = 63.9. For higher horizontal 

 surfaces the section consists of one branch only. For horizontal 

 surfaces corresponding to j^ <C 63.8 atm., the sections also consist in 

 one branch which surrounds the critical loop. 



From X = the bordercur^'e occurs on the front of the jh v, x- 

 surface, but reaches the border almost at the volume 0.008, then 

 occurs on the back where it remains until the point C, and returns 

 to the front. At the point C the osculation plane to the border 

 curve, at the same time the tangent plane to the surface, is horizontal; 

 the projection on the x, «;-plane shows the border curve more and 

 more in its true shape the more we approach tlie point C; whereas 

 in the upper pi-qjection that border curve is seen more and more in 

 an oblique direction and linally in a tangent one, so that it nuist 

 appear flattened, which accounts for the higher order of the border 

 curve in that projection. 



(March 23, 1904). 



