102 PHYSIOGRAPHY. 



Calcareous Spar. 



but having the summit replaced by a tangent plane, d on 

 cl = 153 26'. Four other rhomboids, of the following 

 dimensions: viz. 115 42', 129 54', 151 48', and 156 

 24', derivable from the primary by tangent replacements 

 of its upper edges, the new planes inclining differently to 

 the vertical axis, undergo many of the modifications above 

 described with respect to the primary and the equilateral 

 rhomboids ; but their forms are not common. 



In addition to the foregoing rhomboids, Calcareous Spar 

 presents a great variety of acute rhomboids, of which Fig. 

 100 is one of the most common. It is the contrastant of 

 HAUY. Its localities are numerous. This rhomboid goes 

 through the modifications above described ; and in addition 

 to them, it occurs having the summits replaced by three 

 new planes : in one instance, the new planes resting upon 

 the rhornboidal planes ; and which incline under angles of 

 105 5', being portions of the primary form: and in the 

 other, resting upon the edges and inclining towards the axis. 

 e on e = 65 41'; Fig. 101, a rhomboid still more acute, 

 / on /=60 34'. Fig. 102, the same, with the upper 

 edges replaced by tangent planes ; the contractee of HAUY. 

 /on dl = 112 9' 59". dl on dl = 134 25' 38". Fig. 

 103 is a rhomboid slightly acute, g on g=S7 48. It ap- 

 proaches the cube in form ; and is called by HAUY, the 

 cuboide. It is not common. It suffers the same modifica- 

 tions as the last described rhomboid. Figs. 104 and 105 

 explain the passage of the primary into an acute rhomboid, 

 called the inverted rhomboid, in consequence of its being a 

 complete inversion of the primary rhomboid. P on A= 

 129 13' 53". h on A = 78 27' 47". This form is found 

 undergoing all the modifications above described, and many 



