Vol. 54.] SCHISTS OF THE ST. GOTHAKD PASS. • 373 



investigating the nature of certain forms assumed by pigments in 

 drying, undertook some experiments with substances which readily 

 crystallize. As these will be shortly published/ I restrict myself 

 to stating the general results. In crystallization from a simple 

 solution, the larger and better-developed crystals occur near the 

 edge of the drop, and by this, apparently, their direction of growth 

 is to some extent determined. In the interior they are apt to be 

 smaller in size and more confusedly scattered. In crystallization 

 among a uniformly-obstructing medium (such as gelatine), or some- 

 times from a thin mixture of a pigment like Prussian blue, the same 

 rule generally held near the edge, but the crystals in the interior 

 were larger, better developed, and more definitely grouped," showing 

 a marked tendency to branching and to growing on a ' fern -leaf ' 

 pattern. With a thicker mixture of a pigment (especially if it were 

 slightly coarser) the crystals were yet larger and often more roughly 

 formed, growing in straight lines with frequent bifurcations which 

 diverged at low angles, or forming tufted groAvths ; in fact they 

 approached more nearly to the habit of the actinolite described 

 above.^ But when a still larger amount of pigment was mixed in 

 the solution, then the crystals, so far as could be judged from an 

 examination with reflected light (for the material practicallj^ was no 

 longer translucent), became smaller again and formed a confusedly- 

 matted mass, though in this the ' actinolitic ' habit was still per- 

 ceptible. Thus I believe that the peculiar shapes of these secondary 

 actinolites are in reality a record of past episodes in the history of 

 the rock — that they were formed after it had been largely pul- 

 verized, but before reconsolidation had taken place, and perhaps 

 under considerable pressure. 



V. Connexion of Changes with Earth-movements. 



One question remains: When did this reconstruction oi tn 

 ' Tremola Schists ' take place ? Was it the result of one of the 

 two great earth-movements which produced the existing Alpine 

 chain, or should it be assigned to an earlier date? That such 

 movements also occurred in ])re-Triassic and even in pre-Carboni- 

 ferous times is certain.^ Fragments of schists from the ' Upper 

 Group,' as I have more than once described, occur in the Triassic 

 rauchwacke and can hardly be distinguished from specimens which 

 may be collected in situ in the immediate neighbourhood. But 

 these Tremola Schists also yield some indirect evidence. Though 



^ [They have now (June 24th) appeared in Proc. Roy. Soc. vol. Ixiii, p. 217.] 



^ We might say that the struggle for existence led to a survival of the 

 fittest. 



2 On this subject a considerable amount of literature exists, from which tbe 

 following is a selection : Lehmann, Zeitschr. fiir Kryst. etc. vol. i (1877) p. 453 ; 

 H. J. Slack, Trans. Roy. Micr. Soc. vol. v (1871) p. 1 15: H. Vater (on Calcite), 

 Zeitschr. fiir Kryst. etc. vols, xxi, xxii, xxiv, xxvii (1892-96), five parts. 



■* Alpine Journ. vol. xiv, p. 38, etc.; Quart. Journ. Geol. Soc. vol.xlvi (1890) 

 p. 204. 



