Mineralogy and Geology. 429 
_ The pure mineral from which the carbonate of lime has be 
moved, seems i uniform in composition, and approaches the “felds- 
rs in constitut 
— Bytownite. — Bytowntterde pose to be anorthite with some qua 
or more probably a mixture ifferent feldspars. It is very simtat'ts in 
composition to Genth’s thiorsauite. All those triclinic feldspars interme- 
diate in composition between anorthite and albite, appear to be only 
crystalline mixtures of these two species. See Am. Jour. of Science, 
[2], xviii, 270. . 
esile 
found among the sirata of the Hudson River group in Bolton, Lower 
Canada. Its analysis gave carbonate of magnesia, 60°13, carbonate of 
iron 8°32, silica ith a little chromic oxyd 32:20—100-65. e ser- 
pentines of this formation are believed to result from the alteration of this 
silicious aC in the presence of water. (See Geol. Rep. Canada.) 
lomite—A very compact, fine grained coral etanenes from the 
Island eres han north of Tahiti, furnished me by Mr. Dana from the 
Collections of the U. S. Expl. Expedition, has a fabtieel greater than 
vor; and a density in powder, equal to 2-830. Its analysis gave Car 
bonate of lime 60:50, carbonate of oe 38°77, silica, etc., 0- 
99:57. Another determination gave 38°25 of carbonate of magnesia. 
jog analysis confirms the result of Prof. Silliman, Jr., (this Jour., 
[2], xiv, 82) and shows that the dolomisation took place in the con- 
solidation of the coral material. The rock is the white compact 
snemtane of Matea, an elevated coral island, and resembles much of 
rock found about other reefs. It is as solidra d firm as any Silu- 
2 Set See the writer’s Geol. Report, = also this Jour., xiv, 
—I. D. 
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Gee described by D. D. Owen 
from the gold region, near Nevada city, California. It consists of deep 
yellow, silky tufis, formed by groups of delicate, acicular crystals, coat- 
ing and oie ng the cavities of dark ferruginous quariz. 
This quartz forms numerous —* n micaceous and granitic rocks, 
ina eee where gold bas been 
A qualitative analysis showed in %e It has been as yet impossible 
to obtain sufficient of the mineral for a eros’ or Waeraley analysis. 
3. Reaction of common salt in the format als; M. = erat 
HAMMER.—-On fusing together phosphate of lime Hihe phosphate "i | 
and chlorid of sodium (four parts to one of the phosphate) be seed wa ‘ 
am I oncl 
Spi sie the formation of minerals.—Pogg. Ann., xci, 568. 
