90 Reports and Proceedings — ■ 



of the Lower Greensand." In this valley the Lower Greensand is 

 covered by impermeable calcareo-argillaceous strata (Gault, Upper 

 Greensand, and Chalk Marl), so tliat within an area of ten square 

 miles, from one to two hundred borings have been executed ; and in 

 a great number of instances the bore-holes produce an overflowing 

 sti'eam. The water is slightly chalybeate, its temperature is 51° F, 

 and is generally considered to be very wholesome ; the abstraction 

 from these wells was estimated in 1852 at three to four million 

 gallons daily over the area. 



The distribution of population in relation to water-demand, on the 

 average of 31 gallons per head per day, is shown on a map (p. 575), 

 arranged under 14 sections, and the last chapter treats on the propa- 

 gation of epidemics by potable waters. 



We have attempted to notice generally some of the facts and sug- 

 gestions brought together by Mr. De Ranee, the result of much 

 labour, and which ai'e systematically and usefully arranged. 



To those immediately interested in water supply the volume will 

 be a necessary acquisition, while the general reader will find many 

 interesting points connected with the present state of the water 

 question and its varied sources of supply and distribution. 



The three copious indexes — 1. Of the authors cited ; 2. The dis- 

 tribution of lakes, rivers, etc. ; and 3. The urban sanitary districts — 

 will afford facility for any reference required. 



A more prominent heading at the commencement of each of the 

 thirteen catchment basins, with the same numerals affixed as on the 

 map, and a fuller reference to the works of many of the authors 

 cited, would have been useful. A few typographical errors occur, 

 such as the word " distribution " used instead of " destruction," 

 p. 51,^ River Oak for Ock, p. 215, Ludlow for Wenlock, p. 386, 

 Brentford for Watford, p. 193, and several others of minor import- 

 ance. J. M. 



I^E!I^OS;TS ^^D^ID IPIiOGIEIEIDIIsrca-S. 



Geological Society of London. 



December 21, 1881.— R. Etheridge, Esq., F.R.S., President, in 

 the Chair. — The following communications were read : — 



1. " The Torridon Sandstone in relation to the Ordovician Rocks 

 of the Northern Highlands." By C. Callaway, Esq., M.A., D.Sc, F.G.S. 



The author pointed out that the apparent difference in dip 

 between the l^orridon sandstone and the overlying quartzite in the 

 neighbourhood of Loch Broom was due to some markings in the 

 former which suggested a direction of bedding which was not the 

 real one, and that the one rock passed gradually into the other. 

 The two are perfectly conformable at Strath Auchall, where the 

 junction can be well studied ; also between Uuaport and Strath 

 Kennort, on the north side of Loch Assynt and south of Unaport. 



^ Mr. Topley remarks, " The peat-bogs acted as large sponges, or as compensating 

 reservoirs, but they were being yearly destroyed." — Proc. Inst. Civ. Eng. xlv. p. 90. 



