124 W. A. JOHNSTON 



bined effects of flocculation in sea water, river and tidal currents, 

 and slack water. A leaf bed is shown in sample No. 7 at about mid- 

 length. As it is known from a comparison of soundings made in 

 1859 and shown on the i860 chart with those made in 1919 by the 

 Hydrographic Survey of Canada that sedimentation takes place in 

 the fore-set beds, at the points where the samples were taken, at the 

 average rate of about 20 feet per year, it is obvious that the samples 

 would not show evidence of seasonal banding. It is known that 

 coarse material is deposited oif the mouth of the river during the 

 freshet, and that this is overlain by finer materials deposited during 

 the low-water stage. Hence the bedding probably has in places a 

 seasonal character, but the annual layers vary in thickness, in 

 different parts of the delta front, from a few inches or even less to 

 as much as 50 feet. 



Bottom samples Nos. 9 and 10, shown in Figure i, are from the 

 fine-grained bottom-set beds of the delta, in the Strait of Georgia. 

 Sample No. 9, from a depth of 70 fathoms, is largely silt, and 

 sample No. 10, from a depth of 92 fathoms, is largely clay, which, 

 because of excessive shrinkage in drying, is badly cracked. The 

 samples as mounted and shown in the figures are smaller in size 

 than in the original state because of compression and shrinkage in 

 drying. Sample No. 10 is most compressed, and, judging by the 

 depth of penetration indicated by the mark left on the outside of 

 the sampling machine, is one-half to two-thirds of its original 

 length. The other samples are more nearly representative of the 

 original thicknesses. 



A marked feature of the bottom samples from the fine-grained 

 bottom-set beds is the absence of any trace of lamination either in 

 the beds composed of silt with a mixture of very fine sand, or in 

 the beds composed for the most part of clay. The lack of lamina- 

 tion is due to the well-known effects of flocculation in sea water, 

 which causes the fine silt and clay particles in suspension in the 

 river water to settle to the bottom together when flocculation 

 takes place as the result of the mixing of the two waters. In 

 places also very fine sand settles to the bottom along with the silt 

 and clay. Hence, in the case of the fine-grained materials deposited 

 in sea water, there is a lack of sorting and no definite lamination, 



