552 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [June 17, 



filled up by the Tertiary deposits of the Mittelgebirge region ; or the 

 northern portion may have been lifted bodily and slowly away from 

 that lying to the south of this line, the latter remaining at a com- 

 paratively great depth, and becoming covered by the more recent 

 formations. Be it as it may, no member of the Quader group comes 

 to the surface again until we reach the neighbourhood of Leitmeritz, 

 a distance of between thirty and forty miles further south. 



2. Remarhahle regularity of the lines of parting, especially as 

 regards their horizontal direction. — Wherever the rock is exposed to 

 view, either as forming the precipitous sides of the countless and 

 beautiful ravines which intersect the plateau in every part, and those 

 of the craggy eminences which stud its surface, or in the quarries 

 situated along the banks of the Elbe and elsewhere, it is seen 

 to be divided by fissures running more or less vertically through all 

 the strata, and crossing each other very nearly at a right angle, hardly 

 ever deviating more than 15° from that angle at the point of inter- 

 section. 



Where the clefts toward the top have been widened and rendered 

 conspicuous by the action of water and weather, many of these exposed 

 parts bear no very distant resemblance to old walls of masonry, 

 crowned here and there by square towers and pinnacles more or less 

 worn and disfigured by time. Some of these tower-like blocks are 

 quite detached from the main rock, and rise layer above layer to 

 a height of 200 feet or more, with sides so flat and smooth, and 

 corners so sharp and square, as almost to bear comparison with the 

 ruder specimens of columnar basalt. The distances between the fis- 

 sures may vary from a few inches to many feet. Those which are 

 but a short distance apart ofi'er sometimes a very remarkable ap- 

 proach to parallelism*. Slabs of about 4 inches thick by 8 feet long 



* This peculiar disposition of the lines of parting, which causes the rock to 

 break up into nearly rectangular blocks, has given to it its German name of 

 " Quader," and is of great technical importance as regards the mode of quarrying, 

 which is somewhat peculiar. Gunpowder is very rarely used, the usual manner 

 of operating being to undermine a long piece of the face of the cliif, called by 

 the quarrymen the "Wand" or wall, by cutting out one of the lower strata 

 backwards nearly as far as to the next longitudinal fissure, the length of the piece 

 so undermined being generally determined by the distance between two conve- 

 nient transverse cracks. The whole superincumbent mass, in some cases 150 

 feet high by 200 feet long and from 30 to 40 feet thick, is thus left without 

 support, save what is given by the small portion of the lower stratum left uncut 

 towards the back, and a number, greater or less according to circumstances, of 

 wooden props placed under its fore edge. These are examined from time to 

 time by^the overlooker, who by trying them with a hammer becomes aware of the 

 first indications the undermined rock may give of sinking; the top of the cliff is 

 also examined from time to time. When the mass is not too large, and gives 

 signs of falling before the process of undermining has been carried very far back, 

 the props are cut out by the axe ; but if the piece to be brought down be very 

 large, and, being bound at the ends, requires to be cut under to a distance much 

 beyond the line of its centre of gravity, it gives but short warning, settling ra- 

 pidly on to the props, and would give no time for the workmen to get out of 

 the way, were they to attempt to cut these out in the usual manner ; in such 

 cases they are pierced with auger-holes and blasted out simultaneously, when 

 the enormous mass leans forward and comes to the ground with a crash that 

 is often heard and felt for miles round. 



