138 Notices of Memoirs. 



to be in a line of fault, along which, there has been movement at 

 a comparatively recent period, since the deposition of some fathoms 

 of the superficial deposit. 



(3). The estate consists of Killas traversed by diorite (much de- 

 composed at top). The ores are limonite and magnetite, the former 

 in irregular layers of nodules in a thick mass of sands and clays ; 

 the latter as beds of variable thickness in the greenstone. The 

 hsematite is being worked in an open quarry. 



Tilly, Henry. Particulars of a Thermal Spring at Wheal Seton 

 Mine, in the Parish of Camborne. Be-p. Miners' Assoc. Corn- 

 wall and Devon for 1872-3, pp. 53-56. 



The spring is about 140 fathoms below the surface, and dis- 

 charges 30 gallons a minute, at a temperature of 94° Fahr. The 

 water is moderately clear, but brackish. Analyses are given, from 

 which it is seen that a gallon of the water contains as much as 1072 

 grains of solid matter. 



Collins, J. H. On the Mining District of Cornwall and West 

 Devon, Proc. Inst. Median. Eng. (Birmingham) for 1873, 

 pp. 89-118. 15 Plates (Map, Plans, and Sections). 



The geological structure of the district is first described. The 

 fundamental rock is granite, upon the flanks of the masses of which 

 rests the Killas or slate-rock, which is of variable composition, but 

 generally more crystalline near the granite. The mineral lodes are 

 next noticed : they are most numerous near the junction of granite 

 and slate, especially those of tin and copper, whilst those of lead 

 and iron are often found far off the junction. The different veins 

 are true fissure-veins, often in lines of faults, and they are very 

 often displaced by faulting : their mean directions vary in different 

 parts. Both granite and slate are traversed by intrusive igneous 

 rocks, the elvan dykes occumng chiefly near, and the diorites further 

 off, the granite. The diorites sometimes seem to improve the ore, 

 but sometimes not, whilst the elvans are often very beneficial : the 

 majority of the latter have a general east and west direction, and 

 some have been traced for 12 miles. The method of working the 

 tin and copper mines is then described, and the iron ores and china 

 clay are noticed. 



1874. 



Mello, Eev. J. M. The Midland Coal Field. Pp. 135-140 of " the 



Derbyshire Eed Book," with Map and Section. 8vo. Derby. 



The author notices the probable former continuity of some coal- 

 fields, which have since been separated, through upheaval and de- 

 nudation ; describes the extent of the Midland Coal-field (half of 

 which is concealed by overlying beds) ; notes the estimates that 

 have been made of its probable underground extension eastward; 

 and gives an account of the Derbyshire Coal-measures and of their 

 associated bands of ironstone, with a vertical section of the beds. 



W. W. 



