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Scientijic Intelligence. 
from coppei'plates. From these, he selected one to suit his 
thermometer nearly, but so as to have its division a little too 
near. This approximate scale he stretched, by passing it re- 
peatedly through a pair of steel rollers, until he got it at last to 
fit his instrument with the requisite degree of accuracy, 
III. NATURAL HISTORY. 
MINERALOGY. 
21. American Tourmalines . — Colonel Gibbs of New York, 
in Silliman’s J ournal, has given an interesting account of the 
discovery of green, red, and blue tourmaline, and of beryl, 
in a vein of felspar, which traverses a thick bed of granite, 
contained in mica-slate. The prisms of green tourmaline of- 
ten enclose prisms of red tourmaline ; and in some speci- 
mens there are three crystals of red tourmaline closely aggre- 
gated together, and enclosed in one crystal of green tourma- 
line. In other specimens, there are, in the centre of the green 
tourmaline, in place of the red tourmaline, iron-pyrites. These 
tourmalines are often traversed by transverse rents which are 
filled with felspar. This appearance is not uncommon in the 
schorls and tourmalines of this country, and has been con- 
sidered as a proof of these crystals having been broken across 
by some mechanical force, and afterwards joined together by the 
felspar. This opinion we consider erroneous, because the fel- 
spar which crosses the crystals, is continuous with that which 
forms the mass of the granite ; and as all the parts of the gra- 
nite are of cotemporaneous formation, it follows that the tour- 
malines and their intersecting veins are cotemporaneous. , Some- 
times a thin layer of talc is contained between the outer and 
inner crystal. The largest crystal of red tourmaline found by 
Colonel Gibbs was one-fourth of an inch in diameter, and four 
inches long, and he remarked that they vary from translucent 
to semitransparent. 
22. Cave of Elephanta . — The cave of Elephanta near Bom- 
bay, as appears from specimens in possession of a gentleman in 
Liverpool, is situated in amygdaloidal greenstone, which con- 
tains prismatoidal zeolite (stilbite.) The rock of this cave has 
