| Administrative History | In his paper which was read before the Society on 12 May 1858, George Julius Poulett Scrope described what he proposed "was the probable effect, upon the internal structure of rocks, of the mutual friction of their component parts, when forced into motion under extreme and irregular pressures. He commenced by examining the laws that determine the internal motions of substances possessing a more or less imperfect liquidity, whether homogeneous, or consisting of solid particles suspended in, 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 in 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 coloured matter floating upon water in circular 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 presented by the lamination and occasionally sinuous or contorted structure of the ribboned lavas of Ponza, Ischia, the Ascension Isles, &c., as well as that of gneiss and mica-schist." |