CLAY IRON-STONE ON TllE SOURIS. 



329 



Eiver, is distinguished by nodular masses of clay iron- 

 stone of great richness and in extraordinary profusion. 



The locality where the clay iron-stone was first re- 

 marked occurs fifteen miles from the point where the 

 Little Souris debouches into the Assinniboine. Here the 

 rock consists of a dark-blue argillaceous shale with clay 

 iron-stone layers. The nodular masses vary from eighteen 

 inches to three inches in diameter. They are generally 

 of a compressed elliptical form, and vary from two to 

 nineteen inches in thickness. They form horizontal tiers 

 in the rock, and are often separated by steel-grey and 

 light ash-grey argillaceous bands, which also contain thin 

 seams of clay iron-stone of irregular thickness, and not 

 continuous for many yards. 



Where the river has excavated a passage through the 

 Blue Hills of the Souris, the nodules of clay iron-stone 

 are seen disposed in regular layers, jutting out of the 

 cliff and presenting different colours, varying from steel- 

 grey to reddish-brown and light buff-brown, according to 

 the length of time they have been exposed to the action 

 of the atmosphere and the freedom of the , ore from 

 mechanical admixtures, such as clay, lime, and magnesia. 



A few miles west of the Blue Hills of the Souris, near 

 Plum Creek, the nodular masses of clay iron-stone were 

 everywhere distributed in the river and on the beach. 

 They formed, in fact, the chief constituents of the bottom 

 of the river, and it may be said to flow in this locality 

 over coarse clay iron-stone gravel. The section at the 

 spot referred to, was seventy feet thick, exposed in the form 

 of a nearly perpendicular cliff. The whole of the layers 

 were either tinged with peroxide of iron or of a purple 

 hue, according to the degree of humidity to which they 

 had been exposed by drainage from the prairie or springs. 



Where the clay iron-stone bands were first observed 



