August 20, 1920] 



SCIENCE 



183 



a rejuvenation is here called static rejuvena- 

 tion. 



It may be further stated that the region of 

 the Muscatatook River to the north still pos- 

 sesses just such a local base-leveled plain that 

 existed in the New Albany locality. It is in- 

 ferred that the stream which the Ohio dis- 

 possessed was somewhat near the size of the 

 Muscatatook- White Eiver. This stream pos- 

 sesses a gradient in its graded condition 

 slightly less than one foot to the mile, while 

 the Ohio has a gradient below JSTew Albany 

 slightly less than three inches to the mile. It 

 would appear than such a change in gradient 

 would allow a trenching of something like 90 

 feet, which is approximately the amount of 

 the dissection of the local peneplain in the 

 vicinity of New Albany, using the flood plain 

 as the present local base-level. This figure is 

 derived by taking the difference between the 

 gradients of the Ohio and its assumed pre- 

 decessor from New Albany to Cannelton, a 

 distance of approximately 120 miles. In the 

 lattitude of Cannelton valley filling begins to 

 be rather conspicuous, and this nullifies any 

 difference in the gradients of the former and 

 the present streams, assuming that the valley 

 filling of southwestern Indiana and associated 

 regions took place during the pleistocene. A 

 still further check both on the postulated static 

 rejuvenation and its amount is found in the 

 peculiar gradients of the streams emptying 

 into the Ohio between New Albany and Can- 

 nelton. The gradients are approximately as 

 high in their lower reaches as in their middle 

 and upper courses. This is conspiciously true 

 of Blue River and Indian Creek. Other com- 

 plications however, enter into the full ex- 

 planation of these peculiar gradients, making 

 this a problem in itself. 



The above statement of the conditions and 

 such an explanation are ventured here for the 

 first time. It is thought that the principle of 

 static rejuvenation may have a wider appli- 

 cation than the case here given. The writer 

 would further suggest that its application be 

 made in certain piracy cases. 



Clyde A. Malott 

 Indiana Univeesity 



THE AMERICAN CHEMICAL SOCIETY. 

 II 



COLLOID SYMPOSIUM 



W. D. Harkins and Harry N. Holmes, Joint 

 Chairman 



Some practical applications of colloid chemistry: 

 Jekome Alexander. 



GeXatinous precipitates : Wilder D. BANCROrT. 



The colloid chemistry of soaps: Martin H. 

 Fischer. 



Vegetable tanning as a colloid chemical process: 

 John Arthur Wilson. Vegetable tanning is the 

 reaction taking place between the collagen of hide 

 and the water-soluble matter extracted from cer- 

 tain vegetable materials and known as tannin. Col- 

 lagen is not built up of individual molecules, but 

 of chains of atoms forming a three-dimension net- 

 work with interstices sufficiently large to permit 

 the passage of all ordinary molecules and ions. 

 Under the conditions obtaining in practise, col- 

 lagen has a positive electrical charge and the solu- 

 tion absorbed in the interstices has a difference of 

 potential against the unabsorbed portion of the 

 tan liquor. The tannin particles are negatively 

 charged and the thin film of solution immediately 

 in contact with the surface of the particles has a 

 potential difference against the bulk of the tan 

 liquor, but of sign opposite to that in the case of 

 collagen. This surface film of solution and the 

 solution absorbed by the collagen tend, therefore, 

 to merge, and when this occurs, the positively 

 charged collagen and negatively charged tannin 

 neutralize each other by combination, forming 

 leather. The fact of practical importance is that 

 the potential differences referred to, and therefore 

 the rate of tanning, can be altered without neces- 

 sarily altering the absolute values of the electrical 

 charges. 



Ceramic processes associated with colloid phe- 

 nomena: A. V. Bleiningek. Clays are mixtures of 

 finely divided aluminum silicate, of the type 

 AL032.SiO;2H;0 with granular matter, such as 

 quartz, feldspar, mica, etc., and other colloids like 

 ferric oxide and hydroxide. The particles are of 

 the magnitude of 5fi, or smaller. Clay suspended 

 in water is affected in a pronounced manner by 

 alkalies, salts and acids. The former tend to de- 

 flocculate it, the latter two cause coagulation. 

 Both pheiioiiiena occur in phases. Absorption of 

 the basic ion of salts is characteristic, the acid ion 

 remaining in the dispersing medium. Defloccula- 

 tion is employed in the purification of clays and in 

 the casting process. Measurements of the fluidity 



