Bibliographical Notices. 457 



Pleistocene deposits, of glaciul origin (Drift, &c.). cover almost all 

 the surface of the State, with varying depth to as much as 300 feet, 

 forming most of the landscape features, except where older rocks 

 give rise to larger hills and valleys. The Drift is a heterogeneous 

 series of houlder-beds, gravel-trains, and " more or less sorted over- 

 wash." Nearly structureless deposits of Loess (sands, silts, and 

 clays) occur in the Eastern Counties, and supply abundant material 

 ready lor the clay-works. In most of the Drifts, however, the stones, 

 boulders, and pebbles give trouble, and, like the many calcareous 

 concretions, have to be eliminated in preparation for manufacture. 

 Seven areas of Drift on the map (PI. III.) are referred to five out- 

 spread sheets, lleckoning from above downwards, they are the 

 Wisconsin and its Moraine, the lowan, the Loess, the lUinoian and 

 its Moraine, and the Kansan. At pages 625-5:^4, however, they 

 are described according to the Counties, and from below upwards, as 

 follows : the Pre-Kansan or Albertan of Canada, the Kansan, 

 lUinoian, lowan, the Loess, and the Red Clay or Gambo. 



Chapter VIII. — "Test of Clay-Products" is the subject of 

 pages 538-620 : different kinds of test, and different kinds of bricks, 

 common, hollow, and ]javing, tested by crushing, breaking, by 

 absorption, freezing and thawing; followed by a comparison and 

 summary of tests, with many tables and good diagrams. A 

 Directory of 294 Iowa clay-workers, arranged in Counties alpha- 

 betically (pp. 623-642), e-enerally indicates the firm, the locality of 

 the works, the material used, its geological age, where obtained, the 

 plan of drying, kind of kilns, and the products. An Index of eight 

 jsages, but not very perfect, completes the volume. 



Marijland Geological Surveg. Miocene. [Part I.] Text : pages civ 

 and 543, with Plates i.-ix. [Part II.] Plates x.-cxxxv. 8vo. 

 Baltimore. The Johns-Hopkins Report, 1904. 



The State of Maryland, occupying a district between the Alle- 

 ghanies and the Atlantic, and intersected by two great and broad- 

 mouthed rivers, the Potomac aiul Chesapeake, has a general slope 

 from west to east. Its surface is regarded by naturalists as divisible 

 at the Apalachian region, the Piedmont plateau, and the Coastal 

 plain, each of them continuing through the adjacent States of 

 Delaware and Virginia, and thus constituting the " Middle Atlantic 

 Slope," which comprises in its geology and mineral resources much 

 that is typical of the entire Atlantic border region (page xwiv). A 

 portion only of the coastal plain in Eastern Maryland is here 

 described with the Mid-Tertiary or Miocene strata, of which the 

 surface is mainly comjioscd. These strata and their fossils have 

 largely attracted the attention of American geologists and others 

 for two centuries and more according to the Ribliography at 

 pages xl-lxiv, including the earlier sporadic notices and the more 

 recent systematic and well-nigh exhaustive treatises. 



The relation of the Tertiary deposits of the Coastal Plains to the 

 belt of crystalline rocks in the Piedmont plateau and to the inter- 

 vening limited series of Secondarj' strata is referred to (page .err/). 



