116 



THE GEOLOGIST. 



to produce^ though slowly, the crystals of sulphate of lime, by 

 well known chemical changes ; this must be accompanied 

 with extrication of carbonic acid gas, which if the quantity 

 be sufficient and the production rapid enough, w^ould cer- 

 tainly account for the rising of the earth. Other concomitant 

 circumstances may increase this effect ; these are, that the 

 bisulphuret of iron and carbonate of lime, would occupy 

 more space than in their original state. It also happens 

 that the sulphate of lime (unlike the carbonate of lime which 

 yields its lime) is dissolved by water ; so that the minute 

 crystals of this substance, when the clay is pervaded by 

 water, would be dissolved by it, and the clay rendered addi- 

 tionally loose in its texture, and more readily subject to removal 

 by rain water. It is further to be observed, that this effect of 

 rain water is increased by the difficulty with which it sinks 

 below a certain depth, on account of a hard stratum of earthy 

 matter which occurs at some feet below the surface.'^ 



On the Brighton Raihvay Slip. — This slip occurred in the 

 chalk formation, at a locality where the beds of the chalk 

 are perfectly horizontal, and hence, free from all the dangers 

 above referred to. We have endeavoured to represent the 

 circumstances in Fig. 3, the line A. B. C. D, showing the 



Fig. 3. 



continuity of the beds of chalk. The slip, as will be seen in 



