132 Revieics — Geologi/ of Neicnrk and Nottimfham. 



Manj- points of considerable interest are dealt with in the memoir. 

 Although the Coal-measures occupy a tiny and inconspicuous area at 

 the surface, the question of their underground extent is of great 

 importance ; and Dr. Gibson, Avho deals with this subject, is able to 

 bring the experience he has gained in Derbyshire and North Stafford- 

 shire to bear on the records of trial-borings. It is satisfactory to 

 learn that the divisions established in those districts hold good in 

 JS'ottinghamshire, and that the successive strata can be readily 

 distinguished by their lithological and palneontological characters. 

 Thus four marine bands in the chief coal-bearing series are found to 

 maintain definite positions in the sequence. The divisions are shown 

 in a useful table which gives particulars of tlie thicknesses of the 

 strata and of the depths at which the chief coals occur. Borings 

 have proved that Coal-measures occur beneath the Trias and Permian 

 as far east as Thurgarton, where at a depth of 850J feet the higher 

 and unprofitable measures were reached, and they were penetrated 

 to a total depth of 2,237-^- feet without reaching the Top Hard Coal. 

 That seam was, however, proved to the west, at Oxton at a depth 

 of 2,026 feet and at Gedling at a depth of 1,375 feet; while the 

 results of other borings to the south of Nottingham indicate that to 

 the south and south-west of Thurgarton there is " a buried coalfield 

 of great potentiality ". 



Mr. Sherlock's observations tend to show how closely linked are 

 the Permian and Triassic deposits, as the Permian marl "appears to 

 pass upward gradually into the Bunter by the intercalation of sandy 

 material ". 



Deposits of economic importance are duly noted. The lower 

 mottled sandstone of the Bunter yields moulding sand. The Permian 

 and Keuper marls and the Lias Clay yield materials for brickmaking, 

 while the Keuper marl has been used for the preparation of a top- 

 dressing for cricket pitches and lawns. It furnishes also the important 

 beds of gypsum worked at Newark and Orston. 



The Lower Lias is noted for its hydraulic limestone which is worked 

 in the basal beds at Barnstone. A.t a higher level, in the zone of 

 Ammonites semicostatus, occur layers of ferruginous limestone of no 

 economic importance, but on the horizon of the valuable iron-ore of 

 Frodingham, in Lincolnshire. 



Although the map accompanying this memoir is a Drift edition, 

 the area covered by superficial deposits is remarkably small. There 

 are a few patches of stony loam and gravel that are grouped by 

 Mr. Lamplugh as glacial drift, the stony loam being coloured as 

 Boulder-claj^ This contains Bunter pebbles and occasional erratics, 

 and part of it, west of Cotgrave, may be a direct product of glacial 

 action ; but other accumulations give the impression that they are 

 rearranged relics of once existing glacial deposits. 



Some of the older gravels along the Trent Yalley may, in 

 Mr. Lamplugh's opinion, belong to the closing stages of the Glacial 

 period, but he finds no satisfactory evidence that the river was in 

 existence prior to the great glaciation. 



