^62 



THE GEOLOGIST. 



the latter case, there 'will he more or less separation of the solid and coarser from 

 tlic finer and liqiiid i:)articles, into different zones or layers ; those composed of 

 the former moving less readily than those composed of the latter ; and also that 

 the former will, by the friction attending this process, he tnrned ronnd so as to 

 bring their major axes into the Ime of direction of the movements; and, if 

 susceptible of tension or disintegration, will be elongated or drawn out in the 

 same directicii. 



In illustration of this lavv^, specimens of marbled paper were produced^ being 

 impressions from superficial films of coloured matter fioating upon water in cir- 

 cular or irregular forms, after they had been subjected to motion in one or more 

 directions by lateral pressure; the appearances produced bearing a very exact 

 resemblance'to those i^resented by the lamination and occasionally sinuous or con- 

 torted strnctiu'e of the ribboned lavas of Ponza, Ischia, the Ascension Isles, &c.j 

 as well as that of gneiss and mica-schist. 



The author proceeded to state that the expansion of a subterranean mass of 

 granite by increase of temperature, to which all geologists agree in ascribing 

 the elevation of overlying rocks, oyiust be accompanied by great internal movements 

 and consequent mutual friction among the component parts, and even among the 

 individual crystals ; that if a lubricatmg ingredient, such as water holding silex 

 in solution, or gelatinous silex, be intimately mixed up with the more solid crystals 

 (as there is great reason to believe to have been the case in granite), the friction 

 will be lessened, especially in the central or inferior parts of the mass, where the 

 expanding movement, or intumescence, may be supposed nearly uniform in all 

 directions. But in the lateral and higher portions directly exposed to the resist- 

 ance and pressure of the overlying rocks shouldered off on either side by the ex- 

 panding gr9.nitic axis, the movement will probably have been so predommant and 

 extreme in a direction at right angles, or nearly so, to the pressure, as to give 

 rise to a lamellar arrangement of the solid crystals, in the manner before indicated. 

 In this manner he supposes the foliation or lamination of gneiss and mica-schist to 

 have been produced through the " squeeze and jam" of the lateral and superficial 

 portions of a granite mass expanding by increase of temperature, and the giving 

 way of the overlying rocks, those portions being forced to move in the direction 

 of the lamination v/hile subject to intense x^ressure at right angles, or nearly so, 

 to that direction. The author argues that it is not inconsistent v/ith this view, 

 to suppose that a certain amount of re-crystallisation may have accompanied or 

 followed this lamellar arrangement, in v/hich case also the major axes of the 

 crystals would be likely to take a direction perpendicular to the pressm-e, since 

 the mobility necessary to the crystaUific action will have been freer in that than 

 in any other direction. He likewise points out that the influence of internal 

 friction accompanying motion under extreme and irregular pressures, must have 

 been eqiTally operative in the case of aqueous as of igneous rocks, under similar 

 circumstances of imperfect liquidity, and irrespective of changes of temperature. 

 And he suggests that to this cause may be attributable the internal structure of 

 some veined marbles, calcareous breccias, serpentines, &c. ; as vv^ell as the cleavage 

 of the slaty rocks; as, indeed, the experiments of Mr. Sorby and of Professor 

 Tyndall have already indicated. lie concludes by suggesting to all geologists 

 enuM-rd in the examination of rocks the above mechanical considei'ations, as 

 likolv Lo k';;d to more definite views than at present prevail as to the origin of 

 the uietaiuorphic schists, and the internal structure of many of the older and more 

 disturbed r^M-ks of all characters. 



WaEAVICKSHIKE NATrEAL HiSTOET AND AkCH.EOLOGICAL SOCIETY AND FlELD 



Club. — The council of this Society, in their twenty-second annual report, read at 

 the anniversary meeting on the isth April last, aiinounce numerous and valuable 

 additions to their m.useum and r!brar\' ; but tliey appear, as we gather from the 

 report, to bo deficient in local objc ts and bookLS &c., relating to their county. 

 This is the great defect of most local museums, and that which causes too many of 

 tliom to be justly regarded as mere ciu'iosity-shops. The council, lio^vcvcr, appear- 



