178 Reports & Proceedings — Geological Society of London. 



on the eastern slope of the Sierra Nevada. It is an enclosed basin, 

 so lined by impervious rock-formations that its ground-waters have 

 practically no subterranean outlet. The only outlets for the water 

 are afforded by evaporation from water-surfaces and damp soil and 

 transpiration from vegetation. The alluvial material which forms the 

 "valley fill" varies in size from large boulders to fine clay; and 

 in arrangement it is partly mixed and parti }■ in layers of well-assorted 

 gravel, sand, and clay. It includes materials of the outwash slope 

 and of the valley floor, the underground supply of water being 

 obtained by percolation from precipitation on the surface, from stream 

 channels, and irrigation. The surface area of the valley fill is 

 reckoned to be 230 square miles, and its depth in jjlaces approaches 

 2,000 feet. Allowing an average depth of 1,000 feet, and having 

 regard to tlie porosity of the material, it is estimated that nearly 

 eleven cubic miles of water are stored. It is, however, remarked that 

 the amount to be derived for practical purposes could not exceed 

 that of the natural loss or overflow. 



4. Building and Ornamental Stones of Canada. — Parts i and ii 

 of a Report on these subjects has been prepared by Dr. W. A. 

 Parks and issued in one volume (Ottawa, 1912, pp. 376). The first 

 part consists of a general introduction to the subject, dealing with 

 the cliemical, physical, and geological features of building-stones, and 

 with the methods of quarrying, testing, and pre])aring stone for the 

 market. The materials include granite and other igneous rocks, 

 sandstones, limestones, and slates. Many illustrations of quarries and 

 of machinery are given. The second part consists of a systematic 

 description of the building and ornamental stones which occur in 

 that part of Ontario lying south of the Ottawa and French Rivers. It 

 is prefaced by an outline of the geology of Ontario. Pull particulars 

 are then given of the various building-stones and marbles, illustrated 

 with views of edifices in which particular stones have been used, 

 views of quarries, and maps. There are also a number of coloured 

 plates of limestones, dolomites, and sundry marbles, including sodalite. 

 This mineral, the blue variety of which is regarded as one of the most 

 beautiful decorative stones in Canada, is practically confined to 

 Ontario, inasmuch as it is not known to occur elsewhere in sufficient 

 bulk to be of economic importance. It is found as segregations in 

 a belt of nepheline sj-enite, and can be obtained in slabs up to 4 feet 

 square. In composition, sodalite is a silicate of sodium and aluminium, 

 in which some chlorine is present. 



Geological Society of London. 

 Fehruary 5, 1913. — Dr. Aubrey Strahan, P.R.S., President, 

 in the Chair. 

 The following communications were read : — 



1. "On Two Deep Borings at Calvert Station (I^orth Buckingham- 

 shire), and on the Palaeozoic Ploor north of the Thames." By Arthur 



