﻿568 Revieivs — J. B. Simpson — Northumberland Coal-field. 



and a sinking of the waters to their present level. By this latter 

 action we had the water, so to speak, split up into separate areas. 

 This would explain the similarity in the fauna of the different 

 districts, should it ever be proved satisfactorilj^ to exist, and also the 

 presence of salt lakes in the Trans-Baikal territory, where the 

 waters, for want of outlet, have become gradually supersaturated, 

 until now they annually form a deposit on their shores. 



Most of what I have said about the Baikal, it will be seen, is based 

 on scanty evidence, and must only be accepted until something better 

 can be obtained. When the geology and zoology of these districts 

 have been further investigated, it remains to be seen if we get in- 

 dications as to the origin of the physical features of this part of the 

 world still pointing in the same direction, as those do which we 

 have at present in possession. 



So far, then, I am content to believe that at one time, in this 

 portion of the world, there were inland fresh waters which deposited 

 alluvium, and, as these retired, the Baikal, with its surrounding 

 lakes and lakelets, were left like pools behind a flood. 



I^E^IIE^Vv^S. 



I. — Sections of the Northumberland and Durham Coal-field, 

 By J. B. Simpson, M.E. (Large folding sheet, published by A. 

 Eeid, Newcastle-on-Tyne, 1877.) 



THE times when mining engineers jealously kept their local know- 

 ledge to themselves are rapidly passing away, and it is but rarely 

 now that information of a scientific character is withheld fi'om the 

 public. The publications of the Geological Survey teem with acknow- 

 ledgments of assistance rendered by the very men who, years ago, 

 would have thought it their duty to oppose obstacles to the progress 

 of such work. There are still exceptions, but they are few and 

 far between — survivals, but not of the fittest. The issue of the 

 handsome sheet before us is a case in point. Here Mr. Simpson, 

 well known as one of the most active of North-country mining 

 engineers, and the author of more than one paper of geological 

 interest, has given the world a key to the structure of the great 

 Northern Coal-field, of which it is difiicult to speak with sufficient 

 praise. In the right-hand corner of the sheet an index geological 

 map shows the limits of the field, its chief lines of fault and the 

 lines of section, one N. and S., and the other E. and W., the 

 detailed illustration of which forms the chief object of the plate. 

 This object is attained by means of nearly fifty actual measured 

 vertical pit-sections carefully drawn to scale, and placed side by side 

 in order across the sheet. To the left stands a general section in 

 which every recorded Coal-seam is given and numbered, correspond- 

 ing numbers being used in all the other sections for the same beds, 

 thus enabling one to ascertain at a glance the author's views as to 

 the equivalence of the minor seams. This is perhaps the most 

 valuable feature of the publication. As a datum-line the Low- 

 Main or Hutton Seam has, we think very properly, been chosen. 



