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BROWN : CATALOGUE OF CALCUTTA METEORITE COLLECTION. 
CLASSIFICATION OF THE CALCUTTA COLLECTION. 
Brezina's classification was first employed in his catalogue of the 
meteorites of the Vienna Museum in 1885. In a second catalogue 
published in 189C, it was repeated with certain modifications due to 
advances in the science since the first one appeared. Its latest ex- 
pression is to be found in the Ward-Coonley catalogue for 1904, and 
in a paper by Brezina himself entitled " The Arrangement of (Collec- 
tions of Meteorites" {Proc, Am. Phil. Soc, Vol. XLIII, 1904 
pp. 211-247.). 
In this classification meteorites are first divided into achondrites, 
chondrites and siderites. The achondrites are subdivided into a 
number of groups characterised by more or less definite mineral o- 
gical composition. In the case of the chondrites the subdivisions 
are based mainly on physical appearance and structure after the 
separation of the enstatite-anorthite chonclrites and the siderolites. 
The siderites, after the separation of the lithosiderites are grouped 
into octahcd rites, hexahedrites and ataxites, each of which is still 
further subdivided. As Farrington has shown recently so far as 
iron meteorites are concerned, the system built up by the researches 
of Rose, Tschermak, Brezina and Cohen, is a quantitative one 
{Field Col. Mus., Pub. 1907, Geol. Ser., Vol. 3, pp. 106-110.). The 
same author has lately suggested a quantitative classification for stone 
meteorites, the principles of which are the same as those proposed 
for terrestrial rocks by Cross, Iddings, Pirsson and Washington 
(Quantitative Classification of Igneous Rocks, Chicago, 1903.). As 
many stone meteorites have not been analysed and as the chemical 
composition of a still greater number is but indilJerently known, the 
system cannot be applied universally at present, whatever its merits 
may be, 
