1895.] Mineralogy. 39 
ting the fragile crystals of artificial compounds. It is possible to 
grind and polish a truly plane surface in any desired direction accu- 
rate to within ten minutes of arc. The second device is likewise a some- 
what elaborate one for securing monochromatic light of any desired 
wave-length. This apparatus, which is specially adapted to axial 
angle instruments, goniometers, spectrometers, stauroscopes and micro- 
scopes, secures for the whole field even and bright illumination by 
monochromatic light of any desired wave-length. 
Miscellaneous Notes.—Moses’ describes a simplified method of 
obtaining the projection of the crystallographic axes in clinographic 
projections of crystals.—Luquer* gives in concise form, characters for 
the optical recognition of the common minerals found in building 
stones. The form is a convenient one for use, but some quite mislead- 
ing statements are included, such as the differentiation of quartz from 
nephelene and apatite “by absence of hexagonal crystals.” Apatite 
and orthoclase are both said to have low relief.—George Otis Smith? 
describes two very large scapolites from Eel Lake, six miles from 
Kingston, Ontario, on which the third order pyramid (*f*) (131) is 
developed at both ends of the crystals. The larger crystal exhibits all 
the known forms of scapolite except the base. Smith in the same 
paper examines the monster gypsum crystals of the South Wash, 
Utah, and a prism thought to be one described by Moses" as a new 
form (450), is found to be the known form (340).—Penfield and 
Kreider" show that hydrofranklinite and chalcophanite are identical. 
Hydrofranklinite is not isometric as supposed by Roepper, but rhom- 
bohedral, the combination shown in the crystals being rhombohedron 
and base 
Penfield” has found a crystal of octahedrite among brookites from 
Magnet Cove, Ark. Penfieldite” is described in detail. The mineral has 
holohedral hexagonal symmetry, distinct basal cleavage, and strong, pos- 
itive double refraction. A study is made of the cleavage of albito and 
oligoclase™ in which it is shown that the oligoclase from Bakersville, 
N. C., exhibits two varieties; the one twinned polsynthetically accord- 
1 School of Mines Quarterly, xv, pp. 214-218. 
8 Ibidem, pp. 285-336. 
° Johns Hopkins Univ. Circulars, No. 112, May, 1894. 
10 School of Mines Quaterly, xiv, p. 325; Giani xxi, p. 230. 
11 Am. Jour. Sci., xlviii, pp. 141-143. Aug,, 18 
12 Am. Jour. Sci., xlviii, pp. 113-118, August, 1894. 
13 Penfield, ibidem. 
14 Penfield, ibidem. 
