REVIEWS 361 



By the preceding examination of the geological and physical evidence 

 we have traced the general outlines of the evolution of the present drainage 

 system of East Yorkshire through several successive stages, and we find that 

 its history is intimately bound up with that of the whole of Eastern England 

 since Palaeozoic times. There are local details still waiting to be filled in, 

 and branches of the subject still to be investigated, but it is believed that 

 they will produce no evidence which will contradict the main results here 

 worked out. The division of the physical history of the region since Creta- 

 ceous times into six stages or cycles is based on geological evidence which 

 is practically incontrovertible ; the assumptions as to the original slope of 

 the surface and the deformation of the peneplain are supported by orograph- 

 ical measurements and geotectonic considerations of great weight, as well as 

 by being in harmony with evidence from other parts of England ; and, 

 finally, the theory of consequent and subsequent streams has been established 

 on a firm foundation by Davis and many other workers in the same field. 

 The hypothesis of the secondary origin of the Moorland anticlinal as a water- 

 shed more or less parallel to the oiiginal consequent streams has been found 

 to afford a natural and satisfactory explanation of the behavior and charac- 

 ters of the water courses which it concerns ; and the modifications effected 

 by the glacial period have been interpreted in most cases from direct field- 

 evidence. 



T. C. C. 



The Conveyance of Water in Irrigation Canals, Flumes, and Pipes. 

 By Samuel Fortier. [Bulletin No. 22, Water Supply and 

 Irrigation Papers, Division of Hydrography, United States 

 Geological Survey.] 



The paper calls attention to present practices in the conveyance 

 of water in the irrigated districts in different parts of the arid West 

 and points out ways in which works of this character may be built with 

 greater permanence and at less cost than those now in existence. As 

 the relation of the cost of delivering water to the value of the crop to 

 be raised is the vital question in irrigation, this paper should be of 

 especial value to those in anyway affected by the results of irrigation. 



The report gives a comprehensive review of the various kinds of 

 irrigation canals and ditches, discussing the faults and merits of each 

 and dwelling on such problems of their operation as the effects of too 

 great or too little grade, the growth of aquatic plants and their removal, 

 the accumulation of ice in winter, and the flow of water as affected by 

 the nature and condition of the conduits. 



