Sortas— On the Varioiite and Associated Igneous Rocks. 97 
optical orientation, are probably not always of their original com- 
position, their want of colour suggesting the loss of some ferric 
constituent. 
The felspar has also suffered greatly ; chlorite has everywhere 
invaded it, often forming within it a coarse irregular network 
which, in general form, sometimes reminds one of that taken by 
included glass, so as to suggest the original presence of this 
‘material. Calcite is not infrequently developed in it; and epidote 
y 
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A ag aha 
Hs ATi itn 
RE Gea 
Fie. 1.—Au. augite, Ch. chlorite, F. felspar, Il. ilmenite. 
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abounds, sometimes penetrating and traversing the felspar, some- 
times included within it, sometimes bordering its margins, and 
frequently forming mosaics, when it does not seem to he specially 
related to one constituent of the rock more than another. In thin 
SCIEN. PROC. R.D.S., VOL. VIII. PART I. H 
