Review of Recent Geological Literature. 359 
chondrodite to clinohumite by an increase of one molecule of Mg 2 SiO 4. 
The variation in composition is found to be intimately connected with 
the crystallization, the length of the vertical axis increasing from chon- 
drodite to clinohumite. < ;. 
On the crystallization of enargite. \\\ I.. Y. Pirsson. Amer. Jour. Sci., 
vol. 47. pp. 212-215, March, 1894. < v > 1 1 i t < ■ a number of measurements of 
enargite (Cu3 AsSi r ) crystals from Colorado arc given, also several fig- 
uresof this species which lias been rarely figured in its former descrip- 
tions. Three new forms were observed. <;. 
Relations of tin Lower Menominet and Loieer Marquetti seriesin Michigan. 
]>y Henhv Lloyd Smyth. Amer. Jour. Sci.. vol. IT. pp. 216-223, March, 
1894. These two series have been supposed to be equivalent, in a gen- 
eral sense, by nearlj all the geologists who have worked in this region. 
The author is able to modify this conclusion somewhal and to give it 
more definite shape. The divisions are: 
Menominee. Marquette. 
Michigamme jasper. Jasper banded witli ore. ) Iron 
Slates (principal iron formation;. Magnetite actinolite schist, 'formation. 
Limestone. Quartzyte. 
Quartzyte. 
The author's preliminary conclusions, based largely on the equivalence 
(partly assumed) of three lines of magnetic attraction, are as follows: 
1. The lower Menominee quartzyte, limestone and slates are all older 
than any formation in the Marquette area. 'I. The Michigamme jas- 
per was deposited in a continuous sheet over both districts, and in the 
Marquette constitutes both the iron-bearing formation and. for the mosl 
of the area, the lower quartzyte. '■'<. The principal ore horizon of the 
Menominee has no equivalenl in the Marquette district. (J. 
On the sequence of perlitic and spherulitic structures; a rejoinder to criti- 
cism. By Frank IIiti.ky. Quart, .lour. Geol. Soc, vol.50, pp. 10-14, 1 
plate. 1S!)4. The author replies to a criticism, of Messrs. Barker and 
Marr, of his statement that in a perlitic felsite from Long Sleddale 
/alley, Westmoreland, spherulitic devitrification followed the develop- 
ment of the perlitic structure. Figures are given to show this point, 
both in the rock from Long Sleddale and in an obsidian from Meissen. 
Mr. Rutley sees no reason to alter his conclusion thai sometimes the 
spherulitic structure is later than the perlitic. (i. 
Suffoborit, tin neues krystallisirtes Boratvon Westeregeln. \\\ II. Buck- 
ing. Mathematische u. naturwissenschaftliche Mittheilungen aus den 
Sitzungsb. d. k. preussischen Akad. d. VVissenschaften zu Berlin, ETefl 
ix. Nov. 1893. Some determinal ions of the properties of this new min- 
eral show 1 1) at it is orthorhombic with an axial rat io of «/ : /; : c =0.0190 : 
1 : 0.8100, Five forms are described and five rather distinct habits were 
found. A good cleavage occurs parallel to the unit pyramid, and a 
poorer one parallel to the base. The specific graA it j is from 2 :: s i<> 2. 15. 
The plane of the optic axes is the brachipinacoid. The double refrac 
lion is negative. The chemical composition is SMgSO ,. '.'.M^ :; I*. ,<>,,. 
