768 TRANSACTIONS OP SECTION B, 



of adjusting screws, and altitudes are taten in pairs, the artificial horizon being 

 reversed laterally between each observation and the mean result accepted. Tbia 

 is a special feature in connection with the instrument, and to a great extent 

 eliminates errors. 



2. Notes on the Cartography of the Counties of England and Wales, 

 By Herbert George Fordiiam. 



This paper summarised the results of the author's inquiries into the history, 

 bibliography, and geographical characteristics of the engraved maps of the English 

 and Welsh counties. From the survey of Christopher Saxton, and the publication of 

 his atlas of thirty-four maps in 1579, to the present day there has been a remarkably 

 complete sequence of such maps, which will repay a careful study, both from the 

 point of view of the science of cartography and of that of the artistic side of topo- 

 graphical representation. The author, in examining exhaustively the cartography 

 of two English counties (Hertfordshire and Cambridgeshire), has established the 

 chronology and characteristics of the miips of the whole period here reviewed, 

 and has followed up in detail the history of the publishers, engravers, and topo- 

 graphical writers of the three centuries in their connection with British carto- 

 graphy generally. He indicated the position of the Dutch, Flemish, and French 

 schools of geographers in relation to the contemporaneous work in England at 

 different periods, and established a classification by reference to the initial 

 meridian lines adopted, and to the style and art developed by engravers in this 

 department. He also noticed the principal authors and their best-known works in 

 chronological order, and mentioned, by way of illustration, that in all nearly 400 

 maps have been published of the county of Hertford, of which, however, more 

 than one-half are reprints, more or less altered from the original plates, and may 

 be regarded as duplicates. Any complete collection of the whole series of engraved 

 maps'^of a county in England or Wales, 1579-1900, would contain approximately 

 the same number. The object of the communication was to draw attention to the 

 large and almost unworked field of research which exists in connection with the 

 bibliography and classification of maps from the early period of their production 

 by the engraver's art. 



Bibliography. 



'Hertfordshire Maps: A Descriptive Catalogue of the Maps of the County/ 

 1579-1900. 'Trans. Herts Nat. Hist. Society and Field Club, 1901 to 1907,' 

 Hertford, 8vo, and reprinted privately, with indexes, &c., Hertford, 1907, 4to. 

 • Cambridgeshire Maps : An Annotated List of the Tre- Survey Maps of the County 

 of Cambridge, 1579-1800, with an Appendix containing a List of the Maps of the 

 Great Level of the Fens, 1604-1800.' 'Cambridge Antiquarian Society's Com- 

 munications, 1905 to 1907,' 8vo. ' Cambridgeshire Maps of the Nineteenth Cen- 

 tury, with a List of the Maps of the Great Level of the Fens, 1801 to 1900.' 

 ' Cambridge Antiquarian Society's Communications, 1908,' 8vo. ' Notes sur la 

 Cartographie des Provinces anglaises et fran9aises des seizieme et dix-septieme 

 siecles.' ' Annales du 20"= congres de la Federation archeologique et historique de 

 Belgique.' Gand, 1907, 8vo. 



3. TJie Longitudinal Section of the River Nile. 

 By Captain H. G. Lyons, R.E., F.R.S. 



The increase of cultivation in Egypt during the summer months ha.s neces- 

 sitated an increased supply of water during the low stage of the river, and at this 

 season of the year the equatorial lakes, and that portion of the Nile system which 

 flows from them, alone can furnish it. The Abyssinian tributaries— the Sobat, 

 the Blue Nile, and the Atbara — are in these months discharging little or nothing. 

 As soon, therefore, as the Dervish power had been broken the survey of the Upper 

 Nile was commenced. During the past eight years much has been done, and, 

 among other results, an almost complete line of levelling now exists from the 



