306 ANNUAL OF SCIENTIFIC DISCOVERT. 



forced into motion under extreme and irregular pressures. lie commenced 

 by examining the laws that determine the internal motions of substances 

 possessing a more or less imperfect liquidity, whether homogeneous, or con- 

 sisting of solid particles suspended in, or mixed with, or lubricated by, any 

 liquid, under unequal pressures ; and showed that unequal rates of motion 

 must result in the different parts of the substance, and that in the latter case, 

 there will be more or less separation of the solid and coarser from the finer 

 and liquid particles 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, be turned round so as 

 to bring their major axes into the line of direction of the movements; and, 

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

 the same direction. In illustration of this law, specimens of marbled paper 

 were produced, being impressions from superficial films of colored matter 

 floating upon water in circular or irregular forms, after they had been sub- 

 jected to motion in one or more directions by lateral pressure, the appear- 

 ances produced bearing a very exact resemblance to those presented by the 

 lamination and occasionally sinuous or contorted structure of the ribboned 

 lavas of Ponza, Ischia, the Ascension Isles, etc., as well as that of the gneiss 

 and mica-schist. The author proceeded to state that the expansion of a sub- 

 terranean mass of granite by increase of temperature, to which all geologists 

 agree in ascribing the elevation of overlying rocks, must be accompanied by 

 great internal movements, and consequent mutual friction among the com- 

 ponent parts, and even among the individual crystals ; that, if a lubricating 

 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 expand- 

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

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

 resistance and pressure of the overlying rocks, shouldered off on either side 

 by the expanding granitic axis, the movement will probably have been so 

 predominant and extreme in a direction at right angles, or nearly so, to the 

 pressure, as to give rise to a lanieller 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 granitic 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 

 while subject to intense pressure at right angles, or nea*ly so, to that direc- 

 tion. The author argues that it is not inconsistent with this view to suppose 

 that a certain amount of recrystallization may have accompanied or followed 

 this lameller arrangement, in which case also the major axes of the crystals 

 would be likely to take a direction perpendicular to the pressure, since the 

 mobility necessary to the crystallific action would be 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 equally 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, 

 etc., as well as the cleavage of the slaty rocks; as, indeed, the experiments 



