476 J. 8. Diller — Cretaceous Rocks of No. California. 



Art. LX. — On a peculiar method of Sand-transportation 

 by Rivers / by James C. Geaham. 



It is usually stated that the transporting capacity of a stream 

 is dependent upon (1) the volume and velocity of the current, 



(2) the size, shape and specific gravity of the sediment, and 



(3) upon the chemical composition of the water. There has 

 recently come under my observation, however, a case which 

 does not come under the usual interpretation of these condi- 

 tions. It was a case of the transportation of siliceous sand 

 upon the surface of the water, due to capillary floating. 



It is" well known that a needle can be placed gently upon the 

 water so as to float, the force of capillary attraction producing 

 a surface tension so as to prevent its sinking. This same prin- 

 ciple was being used in removing sand from a bar jutting out 

 from an island in the Connecticut River. 



The erosion was being carried on from the side of the bar 

 against which the current did not strike. It took place by 

 gentle ripple waves splashing up against the sand bar (which 

 was at an angle of about 150° to the surface of the water) and 

 upon the retiring of each, wave a little float of sand would be 

 on the water. At first these were about the size of a silver quar- 

 ter of a dollar, but by the union of a number, some floats would 

 be formed of about six inches square. These blotches were so 

 numerous as to be very noticeable in rowing up the river and 

 could be traced for half a mile or more below the bank, though 

 this bank from which the sand came was but a few yards long. 



If one of the blotches was disturbed by touching or the too 

 violent action of the waves, it would immediately separate, the 

 particles at once falling to the river bottom. 



The above facts seem to me interesting for several reasons. 



(1.) It shows that coarse sand can be floated away by a cur- 

 rent of far less velocity than 04545 miles per hour. 



(2.) It shows a method of removing sand from the lower side 

 of a forming bar which has gotten above high water mark. 



(3.) It indicates a possible explanation of the coarser particles 

 of sand occasionally found in otherwise very fine deposits. 



Art. LXI. — Note on the Cretaceous recks of Northern Cali- 

 fornia / by J. S. Dillee. 



While preparing a geologic map of the northern portion of 

 the Sacramento Yalley, two sections about 30 miles apart of 

 the unaltered Cretaceous rocks upon its western border north 



