1909. 



Reviews. 137 



In Section 2, Professor Cole gives a brief summary of the geological 

 history of the area. Mr. Seymour gives a general account of the rocks. 

 These include epidiorites, lamprophyres, limestones, grits, schists and 

 slates. Sedimentary rocks are much in the preponderance, and are all 

 more or less altered. The chief type is a greenish-gray shale, associated 

 with which are black phyllites, slates, schistose grit, and a small amount 

 of crystalline limestone. The secondary structure is dvie to pressure, 

 thermal action being much less evident. The igneous intrusive rocks 

 have, with one exception, shared in the general metamorphism. 



Part II. gives a more detailed account of the survey. The area was 

 divided into four districts, one of which was allotted to each member of 

 the Survey. The microscopical petrology of all is described by 

 Mr. Seymour, who also is responsible for the excellent photographs. 



Mr. Wilkinson discusses the glaciation of the north-western district. 

 The previous Inishowen memoir mentions the prevailing directions ot 

 striations as S. to N.20^K., and in addition states that the roches 

 moutonn^es with steep western faces give evidence of ice coming from 

 the north-east. Strengthening this conclusion the present survey has 

 revealed deep grooves, having a W.S.W. direction, and in an earlier 

 Boulder-clay at Burnfoot, 8 miles N.W. of the city, basalt, chalk flints, 

 red sandstone, and a fossil shell, Gtyphcea inairva, from the Lias, have 

 been found. In the later Boulder- clay of this district some red granite 

 blocks occur which have a close resemblance to Barnesmore granite. 

 These, together with the deep grooves running in a varying direction 

 from N. 15P E. to N. 10^ E., support the theory of a later ice movement 

 from the south-west. The evidence from the other three districts 

 confirm these conclusions. 



In Part III. the Economic Geology is treated of, Chap. VII. dealing 

 with brick clay, building materials, road metal, water supply, and sea 

 shells. It is interesting to note that whereas formerly the setts for 

 road-making within the city were imported from Scotland and Wales, a 

 suitable granite from Carrigart, Co. Donegal, is now being used. Sea- 

 shells are commonlj^ used for agricultural purposes along the seaboard 

 and are carted several miles inland. An extract from a paper by Samuel 

 Molyneux, about the year 1726, reads that "about 30 years ago they 

 made lime of the shells and manured their land with it; but a poor 

 countryman, that, out of laziness or poverty, had not provided to make 

 lime, threw the shells unburnt on his land ; his crop proved as good as 

 his neighbours ; and the second and third crop better, and all took the 

 hint, and have used them so ever since." 



Chapter VIII. is devoted to soils. Analyses of 28 different kinds have 

 been made by Mr. Hallissy under the direction of Mr. Kilroe. Reference 

 is made in the introduction of this subject to the earlier work done 

 by Portlock in the North of Londonderry. Now that so much attention 

 is devoted to soil physics in England, Germany, America, and Japan, it 

 is gratifying to reflect that soil analyses were carried out in the early 

 part of last century by that distinguished officer. 



I. Swain. 



