TRANSACTIONS OF SECTION C. 349 



Persons quarrying in Syria will find the good compact stone on the surface, and 

 the explanation is the dissolving and depositing action I have described. This 

 state of" things is persistent all over the country, and in places I found a satisfactory 

 explanation of a matter which had long puzzled rae, viz., the formation of marble. 

 When a bed of mud dries it shrinks and cracks ; if the first set of cracks is filled up 

 with mud of some different colour, of cohesion equal to or greater than that of the 

 principal body of mud — you may imagine a second system of cracks filled with a 

 slightly different colour, and so on — you will have such an appearance on 

 making a section parallel to the surface as is shown in the diagram.* Now it 

 is easy to see that if the process of solution and deposition set up by the action of 

 rain water and sunshine tends to cover the country with a solid cake of crystalline 

 limestone, expansion and contraction at the surface continually forms cracks which 

 descend more or less deeply into the mass. According to this, from a plane sur- 

 face there should proceed an irregularly columnar structure. This is observed in 

 pieces of veined marble to some extent, but since the surface is not a plane surface 

 but a changing surface, the columns intersect. Marbles of the kind I am describing 

 are actually in course of formation at the surface of the ground. It is, however, 

 quite plain that many marbles may have been subjected to heat metamorphic action 

 after the veining has been produced. 



It will be seen that all over the surface of a limestone country where the 

 proper conditions exist, there may be formed a universal cake of limestone varying 

 in thickness from 1 to 10 or 12 feet, and in some instances being 20 feet or more. 

 Such a formation will produce large blocks of stone, and it is from such a formation 

 the enormous blocks 14 x 14 x 64 at Baalbek have been quarried. 



7. On certain Geological Facts observed in Natal and the Border Countries, 

 during Nineteen Years' Residence. By the Rev. George Blencowe. 



The basal rocks of the coast are shale, with superincumbent sandstone, which has 

 apparently received its present configuration from subsidence, as the strata dip at 

 an inclination corresponding with the surface, and are cross-fractured. In this 

 sandstone district a square mile of granite protrudes, with a few large loose blocks 

 on one side and mounds of decomposed granite in the neighbourhood. 



The sandstone is succeeded in the middle belt of Natal by deep beds of shale, 

 in thick rusty strata, having in its higher portion blocks of sharp-angled trap 

 scattered on the tops of the hills. 



The northern portion of Natal is a white sandstone capped with trap, which 

 in a high plateau of about fifty miles in length is undisturbed, but in the remaining 

 portion has been scooped out by an abrading force, which has left ridges and 

 isolated hills, corresponding in structure with the plateau, and like it with unbroken 

 horizontal strata. 



At the south-eastern extremity of this plateau there is a district, in and on 

 the edge of Zululand, in which are evidences of violent volcanic action at a 

 period intermediate between the deposit of the sandstone and the varied shale on 

 which it rests. The two most conspicuous evidences of such action are an extinct 

 mud volcano and the turning up beyond the perpendicular of a thick bed of vitrified 

 shale. 



In these newer sandstones coal abounds at various heights, and over a distance of 

 several hundred miles. The water supply of this district is peculiar, coming from 

 the surface of the basaltic trap, and not from the sandstone which underlies it. 



The distinguishing peculiarity of this part of Africa is the presence of isolated 

 hills of sandstone and trap on a high plateau, from which they rise 2,000 feet ; from 

 their correspondence of structure they have evidently at one time been united. 

 The difficulty in accounting for their original construction and their present condi- 



* A diagram was exhibited. 



