ON AN EXPERIMENTAL INVESTIGATION INTO THE FLOW OF MARBLE. 391 
the alteration of which the marble was produced. There are a few little strings of 
sericite between the calcite grains at intervals. While the movements in this rock 
probably took place chiefly before or during its recrystallisation from the finer 
grained limestone, the flattened character of the grains, accompanied as they are by 
twinning and strain shadows, indicate that there have been very considerable 
movements in the rock since its recrystallisation. The structure closely resembles 
that of the Carrara marble artificially deformed at 400° C. A microphotograph of a 
thin section of this rock is shown in Plate 22, fig. 2. It is taken between crossed 
Nicols in polarised light, and is magnified 70 diameters. A part of one of the areas 
of the finely crystalline aggregate above mentioned is seen at the margin of 
the field. 
4. Marble. Near Schaftelen, Switzerland. — This occurrence, believed to be 
Upper Jurassic (Malm) in age, is crossed by the Susten Road near the village 
of Schaftelen. Like that at Andermatt, it has been caught up in the folding of the 
Alps and the rock has been greatly compressed. It is a pure white marble, consist¬ 
ing of a very fine-grained alabaster-like base, in which there are numerous remnants 
of large twisted calcite individuals which are almost entirely destroyed by cataclastic 
action. These have an irregular elongated form, with their longer axes generally 
parallel to one another. Under the microscope the rock is seen to possess a most 
perfect cataclastic structure. The large calcite remnants are traversed by narrow 
twin lines and show most pronounced twisting, with strain shadows and other 
accompanying pressure phenomena. Many of them are seen to be in the act of 
disappearing by being resolved into a mass of smaller grains like those making up 
the mass of the rock. The smaller grains, produced in the way described, are 
flattened in one plane, having the form of little disks or cakes of somewhat 
irregular outline, as can be seen by examining sections cut parallel with and at right 
angles to the foliation of the rock. They do not show twinning, but frequently show 
strain shadows. The fine-grained portion of the rock somewhat resembles No. 5. In 
this rock both cataclastic action and the flattening of the small grains resulting from 
the breaking down of the large ones, by what must be a movement on their gliding 
planes, is plainly seen; both of which are structures exhibited by artifically deformed 
marble. Although the deformation of the calcite in this case is undoubted and 
intense, the twinning lines are not nearly so numerous as in the artificially deformed 
rock. The conditions here have evidently been less favourable to twinning. 
5. Limestone. BiitzistbcJcli, Switzerland. —A limestone of Upper Jurassic age 
(Malm) from the Canton of Glarus and forming a portion of the Glarner Double 
Fold. As shown by Heim, it has been greatly squeezed and rolled out by the 
pressure to which it has been subjected. It is greyish-blue in colour, has a slabby 
structure,And shows no signs of recrystallisation. Under the microscope it is seen to 
be so extremely fine in grain that an enlargement of 500 diameters is barely 
sufficient to resolve it. In structure it closely resembles the finely granulated calcite 
