Reviezus — Coral-reefs in Falceozoic Times. 227 



formations, with their lithological characters. Particulars are given 

 of the geologic occurrence of the underground waters, and of the 

 effects due to the inclination and undulations in the strata of the 

 artesian system, chiefly thick sandstones in the Cambrian and 

 Ordovician. The Cretaceous Sj^stem also contains much artesian 

 water in the Dakota Sandstone, while the Pleistocene or Drift sands 

 and gravels "yield supplies to innumerable shallow wells in nearly 

 all sections and are the most important source of water in the State". 

 The term artesian is rightly used to include not only the water of 

 flowing wells, but also well-waters that rise to a considerahle height 

 within the tube under hydrostatic pressure. 



After the general remarks on the Underground Waters, the subject 

 is treated under eight districts, each including a number of counties, 

 the object being to furnish to each community, so far as possible, 

 information on the artesian water, whether it can be found at certain 

 localities, at what depth it may he reached, through what formations 

 the drill must pass, what mineral compounds (healthful or harmful) 

 the water is likely to contain, how high it will rise, how large 

 will be its discharge, with remarks on its probable permanence. 

 Geologists in this country are chary in giving forecasts of the 

 quantity of water likely to be obtained from a boring, and it is 

 usually thought sufficient to give an estimate of the probable depth 

 at which water would he reached. Indeed, in the present work 

 Mr. Norton advises that "contracts for artesian wells should make 

 provision for drilling at specified rates for several hundred feet 

 bej'Ond the supposedly necessary depth ". At the same time, many 

 official predictions have proved accurate enough for practical purposes, 

 as in cases where the estimate was 700 to 750 feet and water was 

 found at 715, or the estimate was 800 and water occurred at 780, 

 or the estimate was 1,300 to 1,500 and water was found at 1,408 feet. 



One of the more remarkable water-bearing formations in Iowa is 

 the St. Peter Sandstone of the Ordovician, and it is the highest 

 aquifer of the Palaeozoic Series. A map of the State has therefore 

 heen given to show by contours the elevation above sea-level of the 

 top of the sandstone, with contours also of the artesian head of 

 water. Along its outcrops it is a massive homogeneous bed of 

 * millet-seed ' sand. Below ground it is said always to yield some 

 water, and in many places an abundant supply. There is also a Drift 

 map of Iowa, showing the coverings of Kansan, Illinoian, lowan, 

 and "Wisconsin Drifts, also the driftless area. In fact, no pains have 

 been spared to make the volume an eminently practical and reliable 

 work of reference. 



VII. — Did Coral-keefs exist in the PAL^aEozoic ? 



Les becies coralliens existent-ils dans le paleozoique ? By 

 N. Yakowlew, Bull, du com. geolog., tome xxx, No. 201. 

 pp. 847-57. St. Petersbourg, 1911. 



IN this contribution the author states the views he has arrived at 

 on this suhject after more than ten years of geological research 

 among the Palaeozoic rocks of the Ural, Timan, Donetz Basin, and 



