38 Dr Black on some appearances connected with the 



and by altering the weight of these, until, by trial with a tem- 

 porary knife-edge moving round on a collar, the required ad- 

 justment be attained. 



Edinburgh, Feb. 8, 1841. 



On some appearances inferred to have been connected with the 

 Antediluvian Congelation of the Interstitial Water of JRocks. 

 By J. Black, M.D., F.G.S., &;c. Communicated by the 

 Author. 



The escarpments and vertical sections of many sedimentary 

 rocks present several appearances, the more general of which 

 are due to the divisions of the different mechanical and che- 

 mical deposits which are superimposed, one above the other, 

 and form the lines of stratification ; while some others are 

 occasioned by fissures which, more or less regularly, traverse 

 the different beds, perpendicularly to the plane of stratifica- 

 tion, or by the lines of cleavage, which affect either a rect- 

 angular or a diagonal direction across the plane of the several 

 beds. The prolonged fissures are very often extended through 

 the whole stratified beds, and vary from a simple rent to one 

 of several inches in width. In several instances, I have ob- 

 served them so complete and frequent in the sandstone beds 

 of our carboniferous deposits, that the rock has been split up 

 and divided, through the whole depth of the beds, into colum- 

 nar sections, which have stood out on the face of the quarried 

 rock in rough and irregular prismatic columns 30 to 50 feet 

 in height. 



It is not easy, at all times, to account for the formation of 

 these rents and fissures. They have sometimes the appear- 

 ance as if they were the result of desiccation of the aqueous 

 deposit, similar to what is witnessed on beds of clay after a 

 long drought, or on subjecting balls of moist clay to the action 

 of the fire ; but in general they have more the appearance of 

 mechanical commotion. From their being generally observed 

 to be, if there is any difference in the width of the line of fis- 

 sure, wider towards the surface than deeper down in the 

 strata \ and from their occurring more conspicuously in ele-^ 



