380 TKANSACtlONS OP SECTION 0. 



purposes of an engineering work which had necessarily to be based upon the 

 local geology. 



It is sometimes said, and with truth, that the great function of a Survey 

 is to produce a geological map which should be a ' graphic inventoiy,' so far as 

 its scale permits, of the mineral resources, actual and potential, of a country. 

 After all, such a map, even when accompanied with its horizontal section and 

 used by the trained geologist, is a very imperfect instrument by which to 

 summarise and accurately to interpret the results of the surveyor's work. 

 There is so much to e.x;press that a single map will not always suffice. It may 

 be desirable to show not only the outcroiDs of the strata at the present surface, 

 but the thickness of the beds, and even the shape of a bui'ied landscape or sea- 

 planed surface, now nnconformably overlaid by newer rocks. That the 

 Geological Survey are alive to the importance of such work is shown by some 

 of their recent publications. The memoir on the ' Thicknesses of Strata in the 

 Counties of England and Wales, exclusive of rocks older than the Pcnnian,' 

 published this year, is a most valuable compilation, bringing together officially 

 for the first time a vast amount of useful fact, mainly from open sections and 

 borings. May we not look forward to the time when the Survey can issue maps 

 with ' isodiametric lines ' shovv'ing the thicknesses in the case of important beds ; 

 fur example, sheets of productive coal measures, water-bearing bede, and so 

 forth? In any case, we may confidently expect maps that will show by contours 

 the shape and depth of those buried rock-surfaces, whether unconformities or 

 otherwise, which limit strata of peculiar economic value. The Director of the 

 Survey has already given us a foretaste in his valuable and suggestive maps of 

 the Palreozoic platform of South-East England,' and in the contoured maps 

 of the base of the Keuper and of the Permian to the east of the Yorkshire, 

 Nottingham, and Derby Coalfield, and the rock-surface below sea-level in 

 Lincolnshire. - 



Some of the new edition one-iuch colour-printed maps, excellent though they 

 ;ire, suffer by being overburdened with detail already, and we ought to consider 

 whether it is not possible to issue maps of selected districts in series, as is done 

 in the beautifully printed atlases of the United States Geological Survey, where 

 each map of the series shows one particular set of features. 



As regards the Descriptive Memoirs which accompany the new maps, the 

 matter is often so compressed that it is little more than a record of bare fact. 

 \"o one desires the prolixity and the repetition that mar many of the publica- 

 tions of the United States Survey, but we can surely afford a reasonable space 

 for proper description, illustration, and argument; nor, seeing that the memoirs 

 nre permanent records of high scientific value, is it desirable to have them 

 cheaply printed on poor paper. It is said that some Treasury ' Minute ' lays 

 it down that the cost of production of a Government publication must be 

 covered by the anticipated eales of the same; and to comply with this ' Minute ' 

 the public has to pay upwards of 11. for a single geological slieet, because it 

 liappens to include a little detailed geology which adds somewhat to the cost of 

 colouring up. Why not demand that the person living on an island off the 

 West Coast of Scotland shall pay. say, Ss. 6(1. for every letter he receives by 

 post, that being, approximately, what it costs the State to deliver it ? 



We have yet to realise that technical knowledge, of the highest value to 

 the country and obtained at great cost and labour, should be distributed as 

 widely as possible, and at the lowest or even at a nominal charge. I would go 

 further, and put nmch of the technical information in a simple and attractive 

 form. We might even hope, for example, to eradicate the lingering super- 

 stition of the water divining-rod, which is still requisitioned by some public 

 bodies. How admirably clear, simple, and direct is the information on water- 

 supply in the little Survey Memoir entitled ' Notes on Sources of Temporary 

 Water Supply in the South of England and Neighbouring Part of the Con- 

 tinent,' price 2d., evidently produced under the stress of war conditions, and all 

 the better for it. 



' A. Strahan, Pres. Address to Geol. See. 1913. 



' Mem. Geol. Surv. ' Thicknesses of Strata,' pp. 88 and 1 10. 



