68 Canadian Record of Science. 



crystals so formed, which must have constituted a some- 

 what solid rock, was however completely permeated by 

 the magma (which on account of the crystallization already 

 taken place would frequently have become somewhat more 

 acidic), and with this these crystal-free spaces would 

 naturally have been filled. By continued cooling this 

 magma, beginning at the walls, also crystallized out slowly 

 and uninterruptedly, often mixed with minerals which had 

 been formed by special " agents mine'ralisateurs " ; the con- 

 ditions df such crystallization proceeding from the walls of 

 the lumina inwards, must have been somewhat different from 

 those of the former crystallization which took place within 

 the mass of the whole solidifying rock-matter, where the 

 separate individuals must have crowded upon one another, 

 etc. ; hence the ever increasing size of grain, the zonal 

 structure (conditioned by the crystallization from the walls 

 inward), etc. If the magmatic silicate solution were not 

 concentrated to such an extent that the lamina were com- 

 pletely filled by its crystallization, first, open drusy cavities 

 must have resulted, which finally through continued cir- 

 culation might be filled in with minerals deposited from 

 solutions at first still hot but later less and less hot (c. f. 

 the description of the separate phases of vein formation of 

 the veins of the boundary zone on the Langesundfjord, 

 " Die Mineralien der Syenitpegmatitgiinge.") The filling 

 up of the drusy cavities corresponds according to this inter- 

 pretation pretty exactly to the complete vein formation 

 of the pegmatitic veins which occur outside the normal- 

 grained rock mass; the explanation throws light in both 

 cases upon the continuous transition from the rock formed 

 purely by magmatic solidification to the final minerals of 

 the druses deposited from solutions not exactly magmatic 

 (less concentrated). 1 



This successive filling up of the drusy cavities under 

 conditions of formation changing little by little, which in a 



1 The difference between the explanation given above and that of Rosenbusch 

 and others is not so very great, and is, essentially, that I consider the principal 

 filling of the drusy cavities as .also the pegmatitic veins to be magmatic, which it 

 will be difficult to deny in face of the totality of the observations given above. 



