Geology 



of fact a loop of the stream, which had been cut off by 

 the breaking down of an isthmus, such as that we see 

 on the map midway between Wild Duck Lake and 

 Smithford. 



Once the main current of the river was diverted from 

 the loop the portions of its channel near the river would 

 soon become blocked up by the detritus swept in by 

 such water as still flowed through it. Thus it became 

 a lake, and as this part of the plain is still flooded 

 occasionally it will eventually be filled in and become 

 a curved swamp, like numerous others which lie dotted 

 over the alluvial flats on both sides of the river. 



At Horseshoe Bend is the almost complete loop 

 which has already been noticed on the map, and on 

 arrival at the narrow neck of land which alone remains 

 between its two ends, we found that engineering works 

 were in progress, and learnt that a canal was being cut 

 through the isthmus with the object of shortening the 

 journey to Smithford. 



We decided to land here and walk across the 

 isthmus, while the steamer went round the loop, so that 

 we might have an opportunity of examining the section 

 exposed in the canal trench. Here we saw that the 

 material of the flood plain, to a depth of 30 feet, the 

 limit of the excavation, consisted of material similar to 

 that which was exposed in the drainage channel lower 

 down the river, but here there was rather more gravel, 

 and the silt was perhaps a little coarser. 



The stratification of the deposit was by no means 

 simple ; the beds were often wedge-shaped and some- 

 times lenticular, sand, gravel, and fine silt alternating 

 frequently after the manner indicated in Fig. 12. This 



ICO 



