76 



SCIENCE. 



[Vol. I., No. 3. 



have been shaped by erosion, and have a height of 

 from .300 to 500 feet. Although, in general, similar 

 to the archaean of other regions, yet they are especi- 

 ally ricli iu horublendic and pyroxenic rocks; while 

 the highly feldspathic varieties are confined to a few 

 localities, and are usually accessible only at low 

 levels. Baltimore lies on the eastern margin of the 

 broad archaean belt, ' extending from Canada to 

 Georgia, and having the north-north-east trend of the 

 Atlantic seaboard. It is unbroken westward to the 

 triassie area, and is involved in a series of well- 

 marked folds which attained their maximum develop- 

 ment in the Jurassic period. 



In the Baltimore area no formations intervene be- 

 tween the archaean and the Jurassic; and the last 

 is represented only by its highest member, the Weald- 

 en. It reaches from Elkton, in Cecil Co., to beyond 

 Washington, D. C, with an accessible breadth of 

 about thirty miles. It rests dii'ectly upon the archae- 

 an, and is overlaid at various points by the creta- 

 ceous, tertiary, and post-tertiary; although in the 

 vicinity of Baltimore it is covered only by the drift 

 deposits. Tlie thickness of tlie Wealden is not less 

 that! ,500 feet, consisting cliiefly of sandstone with 

 beds of clay and gravel, all derived from the archae- 

 an, and containing vegetable fossils in abundance; 

 although only one animal lias been found, the Astro- 

 don Johnstonii Leidy, a reptile supposed to be relat- 

 ed to the iguanodon. — {Johns Hopk. univ. circ.,Feh., 

 1883.) w. o. c. ["209 



Lithology, 



The hornblendic granite of Quincy, Mass. — 

 Mr. Dodge's paper is valuable as showing in a con- 

 venient form the distribution of the granite and its 

 adjacent rocks. The only otlier tiling new in the 

 paper is the assumption of two different granites in 

 the area mapped, for which lie advances no evidence, 

 although other observers have in general regarded 

 them as local modifications of each other. The paper 

 is, moreover, by no means an adequate representation 

 of wliat is known regarding the ' Relations of the 

 Menevian argillites and associated rocks at Braintree 

 and vicinity ; ' for the autlior does not show tlie rela- 

 tion of tlie known primordial argillite to any other 

 rock (work tliat had been done before by others); but 

 only the relations of some which lie has assumed to 

 be primordial. Tliat these argillites are all of the 

 same age, there is good reason to doubt; for in the 

 Boston basin certain of these are found associated 

 with conglomerates, unconformably overlying otlier 

 argillites," and holding pebbles of the latter. These 

 two different classes of argillites differ from one an- 

 other in their lithological characters ; and that differ- 

 ence, coupled with the association with conglomerates, 

 occurs in Mr. Dodge's so-called Menevian argillites. 

 — (Amer. journ. sc, Jan., 1888.) m. e. w. [210 



Meteorites, 

 The Lodran meteorite. — The microscopic and 

 general characters of this meteorite which fell at 

 Lodran, India, Oct. 1, 1868, were quite fully described 

 by Tschermak in 1870 {Sltzimgsb. akad. winsenscTi. 

 Wien, 1870, Ixi.). Dr. Stan. Meunier finds, on study- 

 ing a section, that it appears to be composed of 

 bronzite, olivine, pyrrhotite, chromite, and grains of 

 metallic iron. If, however, a chip is heated and then 

 suddenly plunged into mercury, the silicates fall to 

 pieces, while the metallic portion is seen to form a 

 very fine network or sponge-like mass. This network 

 is the same as, but finer than, that formed by the iron 

 in the celebrated Pallas meteorite, to which this is 

 allied. Dr. Meunier regards the Lodran meteorite as 

 a true sandstone, having a metallic cement. The 



metallic portion was evidently posterior to the accu- 

 mulation of the silicate grains, which must, before 

 their cementation, have formed a true meteoric sand. 

 Ho does not regard water action necessary to produce 

 such a sand, but thinks, rather, that it was produced 

 by volcanic action. — (Comptes rendus, xcv. 1170.) 

 M. E. w. [211 



Two Japanese meteorites. — Dr. Edward Divers 

 describes two meteoi ic stones supposed to have fallen 

 in Japan about 150 years ago. They are covered 

 largely with the thin black fused coating common in 

 meteorites, but in the interior are light gray in color, 

 earthy, porous, somewhat soft, and interspersed with 

 particles of iron and pyrohotite (troilite). The 

 chemical analysis is as follows: — 



Sp. gr., 3.62 Al 1.00 



^ Na 0.72 



33.18 Mn. . . . 0.57 



Fe 26.13 Cr 0.28 



Si 17.15 Sn. ) „i_ 



Mg. ... 14.02 C ) • • ■ ^■'■^ 



S 2.15 p! . . . . 0.15 



S:l ■ ■ • i-«9 ^ ^ 



Ca. . . . ■ . 1.39 Total . . 99.01 



This is the common composition of the chondritic 

 meteorites. — (Trans, asiat. soc. Japan, x. 199.) 

 M. E. w. [212 



The meteorite of Mocs. — Attention is called by 

 Mr. E. Doll to the form and surface of this meteorite, 

 thinking that it fell in a region that with other mete- 

 orites forms a remarkable zone of falls. — [Verhandl. 

 k.-k. geol. reichsanst., 1S82, 159.) m. b. w. [213 



MINEEALOGY. 



Mispickle. — As a result of simultaneous crystallo- 

 graphic and chemical investigations, A. Arzruni and 

 C. Baerwald have shown that the prismatic angle of 

 this mineral varies, and is accompanied by a corre- 

 sponding variation in sulphur. For an increase of 

 0.00001 in the axis it there is an increase of 0.0236 % S, 

 the length of the axis (L in the varieties investigated 

 varying from 0.67092 to 0.68964, and the sulphur con- 

 tent from 18.051 % to 22.472 % . Thus the mineral does 

 not possess a constant composition, but varies in such 

 a way as to have a definite effect upon the prismat- 

 ic angle. — (Zeilschr. krijst., vii. 337.) s. i.. p. [214 



Minerals from Juliane-haab, southern Green- 

 land. — The following minerals have been described 

 and analyzed by Joh. Lorenzen: — 



Microcline feldxpai: 



Arfredsonite. This occurs in dark cleavable masses, 

 hardness 5.5, G. 3.44, showing brilliant prismatic 

 cleavage at an angle of 124° 22'; also grayish and of 

 a more decomposed appearance. Chemical analysis 

 of the dark cleavable variety showed that the iron 

 was nearly all present as protoxide. The analysis 

 agreed with the formula 11 RSiO;, 4- Ro O3, showing 

 that the mineral holds a position among the amphi- 

 boles which contain a small quantity of sesquioxides. 



Ainigmaiiie. A mineral resembling the above, 

 with prismatic angle 114°, 6. 3.80, is regarded as a 

 distinct species, but no analysis is given. 



Aegirine. This mineral occurs with arfredsonite, 

 and is to be distinguished by the striations parallel 

 to the prism; prismatic angle 86° 58', hardness 5.5-6, 

 and G. 3.63. Chemical analysis showed that the 

 iron exists mostly as sesquioxide, and gave the for- 

 mula Na4 R" R'^j Si 8 O2 6 ; or, — 



R''SiOj > , where <" 

 Ri^4Si, Ojs) I 



I AU : Fe, 



11. 



