612 W. A. NELSON— -VOLCANIC ASH BED IN THE ORDOVICIAN 



less to expect to find any evidence of this ash deposit in those areas that 

 were landmasses at that time, as the many periods of erosion that have 

 taken place since then must have undoubtedly obliterated all such ash 

 deposits. 



This ash deposit, from the fact that at least a few inches of it may have 

 been deposited in all parts of the Lowville Sea, should be carefully looked 

 for, and can be used as a positive base line for correlation work in the 

 entire area where Black River rocks outcrop in the eastern United States. 

 It should also be looked for carefully in all well cuttings from wells that 

 go through Trenton rocks in search for oil, as bentonite fragments are 

 readily recovered from cuttings of cable tools, and their presence shows 

 that the well is through the Trenton and is in the underlying Black 

 River rocks. 



As it is only from those ash deposits which fell in the Lowville Sea that 

 we can look to find a record of the activity of this very ancient volcano, 

 certain suggestions concerning the waters of this sea are hazarded. 



Settling of volcanic Ash in salt and fresh Water 



As a large percentage of the bentonite is very finely crystalline or col- 

 loidal and goes into suspension, an experiment was made to determine 

 the effect of a weak solution of sodium chloride on this suspended matter. 

 A small quantity of bentonite from High Bridge, Kentucky, was mixed 

 with distilled water and allowed to stand five days; the amount of ben- 

 tonite in suspension was decanted and sample number 1 boiled for a few 

 minutes, and after 24 hours all the bentonite was still in suspension. 

 Sample number 2 was boiled for a few minutes with a weak solution of 

 sodium chloride, and after three hours the solution had settled clear. 

 Sample number 3 was added to a cold weak solution of sodium chloride, 

 and the bentonite settled out and left the solution clear in three hours' 

 time. The effect of sea or brackish water on finely crystalline volcanic 

 ash dust can be inferred and account for a comparatively quick settling 

 on the sea-bottom of volcanic ash dust, where the sea water is salt or 

 brackish; but it appears that volcanic ash dust falling on a sea or lake of 

 fresh water would stay in suspension indefinitely, and only the coarser 

 ash particles would settle on the sea-bottom. Such must have been the 

 case in certain Tertiary ash deposits occurring in the Green River beds 

 of Wyoming, Utah, and Montana, in which numerous fossil fishes have 

 been found, and might also account particularly for the altering of cer- 

 tain beds of volcanic ash to bentonite, such as have been described from 



