330 MR. J. E. MAEE OK LTMESTONE-KNOLLS IN [Aug. 1 899, 



He supposes that disturbance was going on all through the period 

 of deposition of the Lower Carboniferous rocks, as well as sub- 

 sequently, and that this caused a more rapid sinking of the sea-floor 

 on the south (downthrow) side of the fault : — ' There was lateral 

 pressure going on in the crust of the earth, and the result of this 

 was to pucker up the ocean-bed into a series of little folds, and here 

 and there the sea-bottom was so raised by gradual movements to 

 sea-level. Then the first result was the breaking-up by the waves 

 of the rock so raised .... A kind of shoal of angular and more or 

 less rounded fragments resulted, and in these shoals arose colonies 

 of animals to whom such a site was suitable. Slowly these little 

 shoals grew up by the continual growth and death of shell-bearing 

 and coral-building animals, and their remains were tossed about and 

 more or less broken by the waves. The resulting debris bound 

 itself together and became a solid limestone-rock. . . . Now these 

 singular deposits differ in their arrangement from all other stratified 

 deposits with which we are familiar in ordinary bedded rock-masses. 

 They grew, many of them, to a considerable thickness, some to nearly 

 50 fathoms in height, but instead of extending indefinitely or 

 thinning out gradually, as ordinary strata do, they are very limited 

 in their extent, and end abruptly all round in a steep slope. They 

 form, in fact, low truncated cones, of which the inner part shows 

 rough horizontal bedding, and the steep sides give outward dips all 

 round . . . . ' 



'It is obvious that if these knoll-reefs commenced on a shoal 

 of fragments broken up by the waves, and grew to 200 or 300 

 feet in height from the accumulation of the remains of marine 

 animals, the foundation on which they rested must have been 

 sinking, so that these animals could still live in that position 

 as regards the surface which was most suitable to them, that is, 

 within the influence of surface-waves ; and when we get reefs like 

 this scattered over wide areas, as is the case, we know that over all 

 the region containing them the sea-bottom was slowly sinking, and, 

 as it sank, the animals kept building up the mounds. Hence the 

 horizontal bedding throughout the middle of these mounds, and 

 the sloping beds round their edges, which simply represent the 

 material, whether the loosened remains of dead animals or wave- 

 broken masses, big and little, of the reef, which ran down the sides, 



until they came to an angle of rest The cones grew up as 



the bottom went down, until either the top was too narrow to give 

 an area of annual growth, or until the rate of sinking was too great 

 for the animals to keep pace with it, and the water consequently 

 became too deep to support such forms under conditions favourable 

 to life.' ' 



I have preferred to reprint this extract verbatim^ in order to avoid 

 any misrepresentation of Mr. Tidderaan's views. It is only fair to 

 state that there is other evidence which he brings forward in favour 

 of his opinion (such as stalagmitic masses in the reef) which I have 

 not quoted. I may refer the reader to the original publications for 

 further information. 



1 * Craven Herald,' Jan. 29th, 1892. 



