96 J. D. Dana on the Isomorphism of Sphene and Euclase. 
Arr. XI1V.—On the Isomorphism of rae and Euclase ; 
by James D. Dan 
Ir is the more common course, in deducing the fundamental 
form from the crystals of a species, to consider the two directions 
of most distinct prismatic cleavage, where such exist, as corre- 
+ eb to the lateral faces of the fundamental prism. ‘I'he 
prominent dupartance, ) the relations of the planes in the crystals 
of sphene become quite simple. 
ere give a table presenting Hy) 
the observed planes in accordance 14#)|12(~)|___[1(2) | 
with this view. O is the basal 22(e)|__/2(n) 
2, -2,—1, belong to the fundamental iP) 
series ; li, ai, are in the seri - 
allel to the orthodiagon ; 4a, wi, in 
that parallel to the ae eT 
and intermediate are forms of the | 
series, m2, m3, m3, 12 and 22 be- 
ing of the first, 73 of the second, and 63 and -33 of the — id 
The table represents a quarter section of the crystal, and is som 
what analogous to a pig gs S projection of it. The faniinennenil 
vertical series is marked off by placing it between heavier lines 
in the table, and so “ale the horizontal series of vertical pris- 
matic planes. For the convenience of comparison, we have also 
given the lettering adopted by others. 
the first figure eter) referring to ~ iy vertical axis ial the paocmid indicating the 
ratio between the two lateral axes. In the expression 1 2, the figure 2 means that in 
parameters of the pla es there i is a ratio of twice the orthodiagonal to once the 
clinodiagonal; and in 6 3, the 3 indicates a ratio of 3 times the clinodiagonal to once 
the orthodiagonal; i in the f former, the 1 signifies once the vertical axi ait, and in the lat- 
ter, 6 a ry 6 times the sam e axis, In the ae) and 2, the second figure is not 
derstood, the ratio between the lateral ari being that of 
“aes the planes are of th I series. The letter i is written in place of 
the sy saliathy & ds), lente signifies that the plane is parallel to the 
vertical has the ratio between the o rthodiagonal and clinodiagonal of 3:1; 
ii is Cooaital rg the vertical axis and orthodiagonal ; 7i is parallel to the vertical axis 
and i i verti i the ratio 1:1 
: axis 
the clinodiagonal, a nd 4 1 efers to the vertical axis, 
