Reviews — Geological Survey of Great Britain. 473 



A rough analj'sis of the specimen sectioned showed that it con- 

 tained, in addition to iron pyrites, calcium and magnesium carbonates 

 and calcium sulphate, the last-named being present in sufficient 

 quantity to form a thick efflorescence when the nodule had been kept 

 for some time. This calcium sulphate is confined to the coal and its 

 marine roof, where it is also abundant,' and to these two beds only, 

 so that its occurrence seems intimately connected with the latter bed. 



A new locality, therefore, can be cited for the occurrence of 

 "coal-balls" or their equivalents, namely, the Alton Coal of Derby- 

 shire, particularly near Ambergate, under conditions which help to 

 confirm the theories enunciated by Professor Stopes and D. M. S. 

 Watson,- namely, that in whatever coal tissue-bearing nodules occur, 

 that coal is overlain by a roof of marine origin, and that the forma- 

 tion of these nodules was contemporaneous with that of the 

 surroundins; coal. 



E.E!^v7"IE"V^S. 



I. — Summary of Pkogress of the Geological Survey of Great 

 Britain for 1917. 55 pp. London, 1918. Price 25. 



IT is a noteworthy sign of the times that this summary of the 

 year's work of the Geological Survey deals almost exclusively 

 with matters of practical and economic interest. The depleted 

 staff has given evidence of great activity, and an immense amount 

 of useful information has been collected, with the assistance of 

 certain specialists who were temporarily attached to the Survey. 

 The most important work carried out was an investigation into the 

 reserves of iron-ore still existing in Great Britain. Every possible 

 iron-field seems to have been very thoroughly examined, and it is 

 estimated that the grand total of ores of all kinds amounts to no less 

 than 11,311,000,000 tons. However, much of this is of very low 

 grade and unlikely to be worked for some time to come. 



The subject of refractories has also engaged much attention and 

 a comprehensive memoir on the subject is in course of publication. 

 The increased demand for tungsten ores has brought about important 

 developments in Cornwall and Devon and new lodes have been 

 reported on. A special examination was also made of Scottish 

 pegmatite dykes as possible sources of potash felspar for pottery, 

 enamel, and other purposes. A magnetic survey of certain parts of 

 England was undertaken with the object of ascertaining whether 

 certain observed disturbances of the magnetic needle were due to 

 concealed masses of iron-ore ; a report on the subject is in prepara- 

 tion. The proposal to construct a ship-canal across Scotland has 

 necessitated investigation of the depth of drift and other superficial 

 deposits along the proposed lines, with interesting results. Good 

 progress has also been made with the publication of memoirs on the 

 Scottish coal-fields. 



' E. D. Vernon, Geol. Mag., 1909, p. 289. 

 - Ibid., p. 181. 



