376 Mr. William Phillips on the OxydofTm* 



23"^, by which it will be seen that the triangular faces correspond 

 with those of 1, 1, fig. 232, which is that of a common prismatic 

 crystal, fig. 27, PI, 16, placed in such a point of view, as most easily 

 shews the section shewn on fig. 194, PI. 24. Each of the eight solid 

 angles of this figure, therefore, is composed of two portions of the 

 common prism, fig, 196; giving, by the common goniometer, along 

 the edges a b c, an angle somewhat more than 112% which, gene- 

 rally speaking, is the same as that / ?n/\ fig. 200 ; the plane 1 on I, 

 over the edge between them, which is that of the comnon prism, 

 also gives an incidence of 90" corresponding with that of the planes 

 1 on 1, fig. 196, That part of fig. 234, comprehended within the 

 dotted lines, is supplied in the made itself, by an elongation pro- 

 ceeding from the upper and lower triangular planes, 



Fig. 235, Ph 26, represents a made, in which two halves of one 

 similar to fig, 218, are attached so as to give an incidence of the 

 planes P on P, which are not visible in the drawing, but which are 

 parallel with the planes P P, which are given, of 112°, 10', by the 

 reflecting goniometer, over the angle between them, corresponding 

 with that of the planes 4 on 4 on the summits of the same figure, 

 and of course with that of the planes 4 on 4 on the summits of 

 fig. 210. 



