Il6 REVIEWS 



much denudation. The youthful lavas have been seen both in Dominica 

 and St. Kitts beneath the stratified gravel beds, but at present it has not 

 been determined whether they belong to the older or newer series. The 

 lower gravels in their succession correspond in position to the Lafay- 

 ette of the continent, and the upper gravels to that of the Columbia. 

 The eruption which raised the cones in St. Kitts and Statia, above 

 referred to, appears to have occurred during the subsidence which 

 gave rise to the upper gravels provisionally regarded as the equivalent 

 of the Columbia series — a mid-Pleistocene formation — and the marl 

 beds thus raised rest upon an incoherent bed of volcanic ashes, con- 

 taining a living fauna. From all facts before the writer it seems that 

 the volcanic ridges owe their origin to volcanic activity which recom- 

 menced about the close of the Pliocene period, and that the eruptions 

 have continued with more or less interruption down to the present 

 day; for we find that the cones and ridges have not become so deeply 

 dissected by rains and streams as would be expected, had their growth 

 not been continued more or less continuously from their rebirth at 

 the close of the Pliocene period to the present year of recorded 

 activity. 



Tlie Marl-Loess of the Lower Wabash Valley. By M. L. Fuller 

 AND F. G. Clapp. 

 The fine silts bordering the Wabash valley have in the past been 

 correlated with the ordinary loess of the region by many geologists, 

 including Owen, CoUett, Wright, Chamberlin, Salisbury, and Leverett. 

 The recent field work of the writers brought out many points of differ- 

 ence in the silts lying respectively above and below the 500-foot con- 

 tour. The lower type, which we have termed "marl-loess," is coarse 

 and frequently carries as high as 30 per cent, of CaCOg, while the 

 common or upland type carries less than 5 per cent. Numerous 

 exposures of distinctly stratified silts, interbedded in a few instances 

 with pebble layers, were noted. Fossils consisting mainly of land 

 species abound, but are not in general regarded as indigenous, as the 

 perfection of the laminae in the fossil-bearing layers points to an 

 absence of vegetation during its accumulation, and would indicate — 

 if the deposit were eolian — the probable absence of both moisture 

 and food, the two chief requisites of the molluscan life. Instead of 

 forming a mantle conforming to surface inequalities, as does the 

 upland loess, the marl-loess frequently occurs as extensive flats or 

 broad, gently sloping terraces, usually burying a somewhat rugged 



