374) On the Isomorphism qfOxamethane aiid Chloroxamethane. 



the measurement of which is rather difficult although the faces 

 are brilliant. The summits are almost always 

 altered ; they are, however, found capable of 

 measurement on very small crystals. 



The result of these measurements is that oxamethane also 

 belongs to the rhombic system. The angle of the two faces 

 which form the bevil at the summit is the same as the corre- 

 sponding angle of the crystals of chloroxamethane. As to the 

 vertical planes, the angles are different ; but it is easy to see 

 that the two forms may be derived from the same fundamental 

 form. In fact, the calculated axes, by taking M for the pri- 

 mitive prism, are 



Vertical axis a = 0-715 



Horizontal axis turned towards the observer 6=1 

 Horizontal axis directed from left to right c = 0*924'. 

 By setting out from these axes, we have, for the notation of 

 the faces and for the calculated value of the angles. 



Notation. 



17. 



Chloroxamethane. 

 V 



O = P 00, 



V 



P = 00 P 00, 



V 

 ; = oo P|. 



Oxamethane. 



V 

 o = P 00, 



V 

 P= 00 Poo, 



M = 00 P, 



V 

 h = 00 P2. 



Calculated angles. 



P : ; = 120" P : M = 132° 43' 



/ : ; on the other side = 120° P : A = 151 " 34' 



P:o =125° 33' P:o = 125° 33' 



The agreement betv/een the observed and the calculated 

 values is such, that it is impossible that the isomorphism can 

 be doubtful. 



