126 Chronicles of Science. [J ee 
clay, and then to have been contorted under the application of force or 
pressure ; while to effect their still greater alteration into the laminez 
of schists, he looks to the further continued action of chemical changes 
amongst the heterogeneous sedimentary materials in selecting and 
combining the different mineral atoms in their proper proportions to 
form the new crystalline masses. - 
Letting alone this last topic, and confining ourselves to the pheno- 
mena of contortion only, if these pebbles were of clay, we could 
understand their being softened; but if they are of limestone, sand. 
stone, slate, or flint, it is very hard to believe they ever were soft- 
ened after they were once solidified. 'The phenomenon is, however, 
exceedingly remarkable, and not yet perhaps clearly explainable. It 
would seem to belong to the same class as the Nagel-Flue of Switzer- 
land, so successfully investigated by Mr. Sorby, or as the nodular 
bands of limestone in the Wenlock Formation, to which attention has 
been drawn by M. La Touche and Mr. Salter. If anyone examines 
the ordinary condition of a conglomerate, or the nature of a sea-beach, 
the more or less rounded pebbles will be found simply piled one upon 
the other, very rarely are any elongated or flat, except when the 
pebbles are of slaty-rocks, and never bent unless they happen to be 
the fragments of naturally-curved strata. In no case are there any 
corresponding lines of contortion, such as shown in the woodcut, which 
represents a section of the Weston Conglomerate, in which the peb- 
bles are drawn out and flattened, and compared by Dr. Hitchcock to 
spheres of clay pulled out into prolate-spheroids ; and the pressure 
of an immense weight might, he thinks, be so continued as to elongate 
a pebble of clay into the resemblance of a lamina of quartz in gneiss. 
He makes intelligible the nature of the Weston Conglomerate by 
supposing that amongst many balls of clay some were plastic and 
- some hard, and that these were then subjected to such a pressure as 
should pull out and flatten all the plastic ones, which would thus 
have their forms modified by the unyielding ones, the plastic pebbles 
fitting on the solid ones like a cap on the human head. “ We find,” 
he says, “among the distorted pebbles cases of this nature. Some 
pebbles have been more plastic than others, and the results are: 
indentations of the harder into the softer ones, curves around the hard 
ones, or the fitting of one into another like a ball into its socket, or 
the ends of the elongated pebbles may only fit upon each other to 
economize space ”—as in the woodcut. 
An example of the first stage of the distortion of pebbles is to be 
seen near Newport, R.I. The lower carboniferous conglomerate at 
Alms House, north of that city, is in a normal state, and consists of a 
mass of loosely-cemented cobble-stones, from an inch to six inches in 
diameter, all round or spheroidal ; but two miles further, at Purgatory, 
there is another mass of conglomerate, nearly of the same age, having 
the pebbles much elongated in the direction of the strike, flattened, 
and often indented, “by being pressed one into the other ;” they are 
sometimes a good deal bent, occasionally in two directions, the whole 
being cut across by parallel joints or fissures, varying in distance 
