384 Mimalayak Mountains. 
Mr. Phiquepal, whom { mentioned in my former ietiers, 
is no doubt by this time on your side of the Atiantic. Ihave 
“capa ratemied you that he carried with him forty or fifty 
large cases of prints, instruments, and books, necessary for 
ie siipidisaian of the system which he teaches. ‘The most 
important objeet is to give, first, a correct knowledge of sub- 
stances, and afterwards words or signs. As he is intimately 
acquainted with the properties of matter, there is every rea~ 
son to expect success; and I hope his example will be fol- 
lowed by other schools, so far at least as to give to children 
ideas of things by their exact representations, instead of the 
vague and undefined method in common use. 
21. Optical Structure of Minerals.—-The optical structure 
of minerals it is well known has thrown much light upon their 
composition. Dr, Brewster has lately examined a specimen 
of the lithion mica of Prof. Gmelin, and has ascertained that 
these plates are composed of erystals with one axis, united 
to erystals with two axes. Now as all the uniaxal crystals of 
mica yet examined differ in chemical composition from tho 
biaxal ones, Dr. Brewster recommends Prof. Gmelin to de- 
tach all the uniaxal parts if-possible from the biaxal plies and 
to make a separate analysis of both. If he finds what analo- 
ey es Se us to expect, that these two portions are chemi-~ 
eally different, the result will be a most important one, both 
for Bin and analytical chemistry. It will set aside all 
analyses of minerals, where it is likely that the body analysed 
has not been an individual crystal, and it may thus Peat 
wpon a firmer basis the law of definite proportions, = 
22, Himalayah Mountains.*—U pwards of 25,749 feet bare 
been stated by two eminent mathematicians, Captains Hodg- 
son and Herbert, as the elevation, trigonometrically ascertain~ 
ed, of one of the Jowahir peaks. Calculations have been usu- 
ally fe founded either upon comparison with the medium height 
barometer in Calcutta, or at the level of the sea 
sine a miles off) during the month in which the 
tion on the mountain was made. Even where contempora- 
neous observations are obtained, have we ascertained that 
from a paper by George Govan, M. D, in Dr. Brewster's 
. a 
Edin. Jour. of Science, Vol. I 
