150 Physical Geography. 



somewhat tufaceous in character, as if the layers, which 

 are unfossiliferous, had been deposited from solutions. 



In other parts of the district, along the coast of 

 Durham, large tracts of the limestone consist of vast 

 numbers of ball-shaped agglutinated masses, large and 

 small, and I have observed in limestone caverns, in pools 

 of water surcharged with bicarbonate of lime, that 

 sometimes precipitation takes place on a small scale 

 producing similar nodular bodies. It is notable also 

 that when broken in two, many of the balls are seen to 

 have a radiated acicular structure, that is to say, from 

 the centre rudely crystalline- looking bodies all united, 

 radiate to the circumference. In other places we find 

 numerous bodies radiating in a series of rays that gradu- 

 ally widen from the centre, and are unconnected at their 

 outer ends, which remind the spectator of radiating 

 corals. There is, however, nothing organic about them, 

 and I do not doubt that they owe their growth to some 

 kind of crystalline action going on at the time that the 

 limestone was being formed. 



The occurrence of gypsum in the marly strata of 

 the Permian series, helps to the conclusion that they 

 were all deposited in inland waters, for it is impossible 

 to conceive of pure sulphate of lime having- been thrown 

 down from solution in the ocean. 



In these views I do not stand alone, for similar con- 

 clusions are held by Dr. Sterry Hunt, as shown in Sir 

 William Logan's ' Geology of Canada,' and Professor 

 Dana in his ' Manual of Greology.' 



The chemical argument is not, however, what first 

 led me to suspect that the Permian Magnesian Lime- 

 stone was deposited chiefly from solution, in an inland 

 salt sea, but rather the poverty and dwarfed character of 

 the fauna alone, while I soon saw that the chemical 



