814 The American Naturalist. [October, 
siderites, adds to the thirteen forms of that mineral previously known 
the three rhombohedra (0332), (3034), and (1012).—Termier and 
Richard” conclude from their study of crystals of Ca,P,O, occurring 
in the slags of the iron works at Kladno, that they are poendopttbo 
rhombic, composed of monoclinic lamellæ. Measurements of the ap- 
parently orthorhombic form agree well enough with those of Miers to 
show that both had to deal with the same substance. The specific 
gravity is 2.93-3.1, mean index of refraction, about 1.64. For red 
light, 2 V = 20° (?), and for blue light it is about 40°.—O. Norden- 
skidld" finds edingtonite from Bédhlet, Sweden, to be orthorhombic 
hemihedral instead of tetragonal hemihedral, as previously supposed. 
Sp. G. = 2.776, plane of optical axes = 010, negative bisectrix parallel 
to the vertical axis, 2 V for lithium light = 52° 47’, for sodium = 52° 
55, and for thallium 53° 10’. The indices of refraction for the above 
kinds of light are also determined. The mean index for sodium light 
is 1.5492,and the double refraction is .016. In conclusion, the simi- 
larity of form with that of mesotype is shown by the axial ratios : 
Edingtonite a:b: c = .9872: 1: .6733 
esotype a:b: 2c = .9785:1:.7072 
—Goldschmidt* figures and describes a projection goniometer by 
means of which the position of crystal faces is projected directly upon 
paper, thus doing away with the reading of angles and with trigono- 
metrical computation. The instrument seems to be in many ways con- 
venient, but does not give the highest degree of accuracy. A contact 
goniometer of similar action is also briefly mentioned. 
PETROGRA PHY: 
Geology of Point Sal, California.—The geology of Point Sal, 
the extreme northwestern corner of Santa Barbara County, California, 
has been carefully worked out by Fairbanks’ with special reference to 
the igneous rocks found there. The sedimentary rocks constituting the 
point and the adjacent country are of miocene.or later age. They 
16 Bull. Soc. Fr. Min., XVIII, pp. 291-295, 1895. 
1 Bull. Soc. Fr. Min., XVIII. pp. 395--398, 1895. 
18 Zeitschr. f. Kryst., XXV, pp. 538--560, 1895. 
1 Edited by Dr. W. S. Bayley, Colby University, Waterville, Me. 
2 Bull. Dep. Geol. Univ. of Cal., Vol. 2, p. 1. 
