96 Pentti Eskola. i (LXIT z ; 
varieties richest in alumina of all the rocks of the sviato- 
nossite series. s 
The graphite contained in the pegmatites of the sviato- = 
nossite is a fact giving added strength to the above theory. 
of the origin of the sviatonossite from the granite magma 
reacting upon the graphite-bearing limestone. 
The theory of the origin of the sviatonossite outlined 
above is, in all essentials, agreable with Daly's theory of the 
alkaline rocks, which in the later times has produced so many 
apologists, Adams and Barlow having first called attention 
to the apparent field-association of limestone and nephelite-: 
syenites in the Haliburton and Bancroft areas in Ontario ?). 
If the mutual reaction between the sviatonossite magma 
and limestone had proceeded a step further, lenads would 
hawe crystallized out from it and by the settling down of the 
garnet crystals a true nephelite-syenite would have arisen. 
It is doubtful, if nephelite-syenites originated in this way 
have ever been observed, for the complex should then be 
accompanied by igneous andradite-pyroxene rocks. . The cro- 
maltite of Cnoc-na-Sroine really presents such an »ultramafic» 
rock, and its origin is explained by Shand just in the way 
pointed out 2) above, but there are no normal nephelite-sye- 
nites in the complex. The gravitative differentiation probably 
never furnishes such a complete example, in which a mineral 
once crystallized out may be carried away completely. 
But nature has many other methods for producing alkaline 
rocks by interaction between magmas and limestone. In some 
areas direct assimilation of calcium carbonate may have 
taken place-and the mafic lime-rich silicates, such as diopside 
and hornblende, resulting from the reaction within the hybrid 
magma, are carried away by the gravitative way. At present, 
however, no certain cases of a large-scale assimilation of . 
limestone have been recorded, so far as my knowledge goes. 
Certainly more important is the contact-action, whereby 
/ 2) Frank D. Adams and Alfred E. Barlow, Op. cit. (Geol. Surv. Canada, 
Mem. 6, 1910). 
?) S. J. Shand, loc. cit. (Transact. Edinburgh Geol. Soc. IX, 1910), p. 394. 
That the cromaltite is not to be explained as a skarn, seems to me evident 
from its minerals which are those found also in the borolanite (note 
aegirite-augite). 
