854* Analysis of Scientific Books and Memoirs. 



jected between the folds of the lower schists ; and into any crevices or 

 fractures formed in them. At the same time, the upper strata recede, 

 in a lateral direction, from the axis of elevation, slipping down the inclin- 

 ed planes of their stratification, by the influence of gravity, and become 

 also more or less bent and folded together, owing to the resistance 

 opposed to this subsidence, by the inertia of their distant unelevated 

 parts. Curvatures* and replications could, however, only take place where 

 the strata were in a semi-solid state, or where the peculiar structure of 

 the rock was favourable to the partial mobility of its parts ; and this ap- 

 pears to have been particularly the case with the laminar and schistose 

 rocks, whose parallel plates of mica are enabled to slip, with more or less 

 facility, over one another ; such rocks appear to have often suffered an ex- 

 traordinary degree of replication. By the subsequent destruction of the 

 extreme flexures of these folded strata, they seem, to a traveller passing 

 across their edges, to alternate repeatedly in a recurring series. Where 

 the induration was more complete, or the structure of the rock unfavour- 

 able to flexibility, as in the compact and massive limestone formations, 

 numerous fractures, fissures of all sizes, often of great width, will have 

 been broken through them, and the intervening masses of strata more 

 or less dislocated and disturbed in their position, sometimes, perhaps, 

 left in isolated patches on the summit or flanks of the protruded crystal- 

 line rocks. This appears to have been the origin of the insulated py- 

 ramids of dolomite, which rise from the great porphyry district of the 

 Tyrol. Indeed, any one acquainted with the aspect of the limestone 

 formations of the whole range of the Alps, will acknowledge, that, in 

 this irregularity of position and inclination, their perpendicular escarp- 

 ments, and chasm-like vallies, these vast masses of strata accord precise- 

 ly with what might be expected from a mode of elevation, such as is 

 here attributed to them. Thus, of the fissures broken through the 

 elevated strata, those which descended sufficiently in depth, and open- 

 ed into the inferior lava-bed, occasioned extravasations of this substance, 

 producing dikes, &c. others which were too narrow and intricate to al- 

 low of their occupation by the intumescent matter, were yet permeable 

 to the vapours that rose from this subjacent and intensely heated mass, 

 bringing with them both earthy and metallic sublimations, which would 

 be deposited on the sides of the fissures, together with fragments bro- 

 ken from these sides, or fallen from their upper parts, whence the 

 mineral veins. Those fissures which did not communicate with the heat- 

 ed lava-bed, were filled in part, or altogether, by rubbish alone, and these, 

 are the faults or slips of miners. The formation of calcareous and other 

 breccias, scai. veined marbles, is accounted for by the smallest of these frac- 

 tures ; the still unconsolidated juices of the rock oozing into its cracks and 

 crevices, and filling them with a deposit of finer matter. The quartz 

 veins of the arenaceous and micaceous rocks are attributed to the same 

 process. 



The author goes on to draw a distinction between the primary range, 

 or axis of elevation, along which the overlying strata were burst open and 



