May 31, 1895.] 



SCIENCE. 



605 



observation and pliysiological tests prove ; 

 uor is such preforuiation necessary if a me- 

 chaoiical hypothesis is adopted. 



JouN A. Ryder. 

 (To be concluded .) 



CCHREXT NOTES OX PHYSIOGRAPHY ( VIII.) 

 Crowley's ridge. 

 Crowley "s Eidge, rising above the al- 

 hivial lowland of the Mississippi in Missouri 

 and Arkansas, has long been a subject of 

 discussion. Branner (Geol. Surv. Ark., 

 Ann. Rep., 1889, ii., p. xiv.) has suggested 

 that the lowland to the west of the ridge 

 was excavated as an early path of the Mis- 

 sissippi, from which it was diverted into 

 its present course east of the ridge by the 

 Ohio; but it is difficult to uudei-stand how 

 the smaller of the two rivers could divert 

 the larger one. A new explanation of the 

 ridge has recent] j' been oftered by C. F. 

 Marbut (Proc. Boston Soc. Nat. Hist, xxvi., 

 189.5), to the eifect that the ridge is 

 homologous with the C'hunnenugga ridge of 

 Alabama, and that it belongs to a familj- of 

 geographical forms frequently found on 

 coastal plains during the matui'e stages of 

 their development. These ridges or up- 

 lands uormallj- run parallel to the coast 

 line : they mark the outcrops of compara- 

 tively resistant strata, dipping toward the 

 coast; they descend inland by a relativelj' 

 rapid slope, often strong enough to be 

 called an escarpment, towards an inner 

 lowland which has been eroded on an 

 underlying and weaker member of the 

 coastal formations; they descend more 

 gently on the coastal side. The inner low- 

 land is drained bj- longitudinal streams, 

 which enter transverse streams that cut their 

 way through the ridge or upland on the \\ay 

 to the sea. In a region of uniform ui)lift 

 all these features of relief and dniinage liave 

 a regular rectangular system of trends: but 

 where the former shore line or the uplift is 

 irregular the trends will depart more or 



less from a rectangular towards a curved 

 pattern. Marbut regards Crowley's ridge 

 as a portion of an inland-curving ridge of 

 this kind. The master stream of the region 

 is the Mi-ssissippi. which bisects the inland 

 curvature of the ridge. The upland along 

 whose eastern base the Tennessee river flows 

 northward in an adjusted subsequent course 

 forms the eastern part of the curve; while 

 Crowley's ridge forms the western part. 

 The lignitic strata by which the ridge is de- 

 termined weaken south westward, and hence 

 the ridge soon disappears in that direction. 

 The lowland west of Crowley's ridge, 

 ascribed by other writers to erosion bj' the 

 Mississippi, is explained by Marbut as com- 

 parable to the lowland on the inland side 

 of the Chunneuugga ridge of Alabama, and 

 the rivers which follow this lowland are 

 thought to be adjusted subsequent rivers. 



THE CUSPATE CAPES OF THE CAROLINA COAST. 



The systematic repetition of certain 

 features in Cape.s Hatteras, Lookout and 

 Fear is explained by C. Abbe, Jr. (Proc. 

 Boston Soc. Kat. Hist.. xx\-i., 1895) as the 

 result of a number of backset eddying cur- 

 rents, turning from right to left between the 

 Gulf Stream and the coast. The generally 

 .southward movmeut of the sands along the 

 shore being well known, some special exi)lan- 

 ation is needed for the acutely pointed capes 

 between the smooth concave curves of the 

 sand bars. Although this is a conspicuous 

 feature of the coast, it seems to have been 

 little considered. Shaljjr, in his recent 

 general account of Harbors (U. S. Geol. 

 Survey, 13th Ann. Kept.. 1893. ISO ), sug- 

 gests that the greater inflow of the tides 

 in the middle of the curved bays between 

 the capes would cause a lateral current in 

 either direction, and that the cusps would 

 form where the outward flow from two 

 curves became confluent; but this is conti-a- 

 dicted not only by the general southward 

 movement of sands along the shore, but also 



