Frof. Judd — The Earliest Engraved Geological Maps. 101 



While constructing the small manuscript geological map of England 

 and Wales, William Smith became convinced, as he tells us, that "the 

 intricacies in the marginal edges " (of the strata) " were such that 

 I found to mark point by point, as the facts were ascertained, was 

 the only way in which I could proceed safely. My experience in 

 what I had done upon the Somersetshire Map was sufficient to 

 convince me of this, and that to make a map of the strata on a scale 

 as large as Gary's England (five miles to an inch) with sufficient 

 accuracy, much of it should first be drawn on a larger scale." 



The delay in publishing the work certainly resulted in the Map of 

 England and Wales being much fuller in detail than it would have 

 been if issued in 1801. Instead of the eight colours used in the 

 early map, we find no less than twenty colours employed in the 

 engraved map of 1815 ; and three other spaces were introduced into 

 the legend, though left uncoloured. We also find separate indications 

 used for collieries, lead-mines, copper-mines, tin- mines, and salt and 

 alum works, while the distribution of the great areas of granite 

 and other igneous rocks were fairly indicated. One very important 

 feature of the map was the inclusion of a section from Snowdon 

 to the south-east of England, in which the superposition and dip of 

 the strata and the formation of escarpments and intervening vales 

 by the agency of denudation are clearly illustrated. 



The chief defects in the famous map of William Smith, which 

 was at last published on August Ist, 1815, were as follows : — The 

 representation of the Tertiaries was very inadequate, no indication 

 of the Crags being given, the Isle of Wight Tertiaries, the Bagshot 

 Beds of Southern England, and the Boulder-clays of East Anglia 

 being all confounded together, and the relations of these to the 

 London Clay being left obscure. The Wealden area was altogether 

 unsatisfactorily treated, the argillaceous strata being coloured as 

 " Oaktree Clay " and the arenaceous as ironsand (Lower Greensand, 

 etc.). Lastly, the Jurassic estuarine strata of North Yorkshire were 

 confounded with the " carstone and ii'onstone " of the South-East of 

 England. On the other hand, it is interesting to note that Smith 

 had already learned at this early date the existence of strata lying 

 between the Old Red Sandstone and the slaty rocks of Wales and 

 Cumberland. These have a tablet assigned to them in his legend 

 with the description " various alternations of hardstone, limestone, 

 and slate," though the information he possessed was not sufficient to 

 enable him to extend proper colours for them to the map. This is 

 probably the earliest notice of the strata afterwards made so famous 

 by the researches of Murchison and his coadjutors. 



The period following the issue of his great geological map was 

 one of much activity to William Smith, In the year which witnessed 

 the publication of the map (1815) he issued " A Geological Table of 

 British Organized Fossils which identify the Courses and Continuity 

 of the Strata " ; and in the following year he prepared the first part 

 of his " Strata identified by Organized Fossils," only four parts of 

 which out of the seven contemplated ever saw the light. In 1817 

 Smith published an enlarged section from Snowdon to London. 



