* _ ve A 
ys 114 < - Sbientife ye ntelligence 
_ of several other varieties, I have ‘wiany portions of different ages, all of - 
which have exact resemblance. Of the Calymene Blumenbachii, I : 
perfect, and in them I find no change in appearance. Thus it would 
appear that in our varieties, at least, we have no metamorphosis of the 
earliest of the moving animals. However, I have not seen his work, 
and “ hc of it may be too short to give a correct idea of what 
he m eo 
Genelia Montgomery Co., Ohio, April 18, 1850. oe 
_ 2. Observations on the Mica Family ; by J. D.Dana.—The Mica fam- oe 
for a trimetric mica, Margar odite ae a-second coat or oblique mica, 
etc.; and it is probable that several other species besides those now . 
known, are yet to be distinguished. . 
The following observations on the different kinds of mica are. -main- : 
ly from the volume just referred to. : 
Rammelsberg in his 4th Supplement (p. 76) has calculated anew the 
sean > = ifm nia 
several analyses of muscovite, and lays down the formulas of the va- f 
rieties. But by some oversight, he makes the ratio for the oxygen of the Sg 
protoxyds, poroxyds and silica, L : 12: 15 equal to $: 9: 12,a sif 4: 
: 4; and the formula deduced is that he on the aigici 
ratio. As the point is of some importance, we give here the ratios from ‘a 
¢ his calculations, making the oxygen of the alumina 12, for better com- 
ac ratio to the other ingredients: while the ratio between the perox- 
and silica, since it is much nearer oe is not liable to such 
iocicaaka The results are as follow 
R 8 “Bi 
63 : 18-622: 24-68 — 1:05: 12: 15°91. 
42: 17°76 + 23°95 — 0°96 : 12 : 16°18. 
39 : 18:56 : 24-01 — 0-90 : 12: 15°52. 
56: 18-54 924-09 — 1:07: 12 : 15°59. 
44 : 17°89 : 24°52 — 0-97 : 12: 16°45. 
Tels P2E97 = 4 STS? 6871. 
ai Rose - 
i 
Fahlun, Rose, 7 
mua I: 
¥ 
i 
Ochotsk, R 
Zsidovacz, Kussin, 
Mean, excluding the last, 0-98 : 12 : 15-93 
Mean, including ee last, 1-005: 12 : 16-06 : 
Corrected. ¥ 
ean therefore of the ‘dea analyses from which Rammelsberg ; 
deduces | his ratio is very close 16, an ene analysis be 
yses co more nearly with Fl : 12 : igthan 1 = i e.10. 
formula Si, adopted By is ght is not therefore sustained 
_ by the analyses. 
