446 Professor J. W. Judd—Wm. Smith's MS. Maps. 



to the north, supplemented by persevering inquiries in every quarter 

 where he could hope to glean information. 



The idea of a general geological map of England appears to have 

 been generated in the mind of "William Smith upon the occasion of 

 the famous post-chaise journey in 1794; but during his five years' 

 close confinement to practical engineering on the Coal Canal, his 

 much-wished-for opportunities of collecting observations enough 

 from the ranges of the different strata to make an accurate delineation 

 of the stratification throughout England were, as we have already 

 seen, suspended. 



The leisure which followed his resignation of the post of Eesident 

 Engineer to the Coal Canal was spent by Smith in endeavouring to 

 carry out his great scheme. He says that he " wasted much time in 

 poring over maps, in contriving how the ranging edges and planes 

 of the diiferent strata could best be rendered intelligible ; models 

 were thought of, and one small map was cut along the edges of some 

 of the strata with a view of defining their extent, and of showing 

 how one stratum was successively covered by another." He adds 

 that " some small maps of England were spoiled by speculating 

 on the ranges of stratification without sufficient data. The intri- 

 cacies in their marginal edges were such that I found, to mark 

 point by point, as the facts were ascertained, was the only way in 

 which I could safely proceed." 



The result of Smith's speculations as to the best way of repre- 

 senting the outcropping strata upon maps is seen in the method 

 which he finally adopted, and which was first illustrated in the 

 manuscript maps of 1799 and 1801. The base of each formation 

 is shown by a band of colour which is shaded upwards towards the 

 next succeeding formation. The colours adopted in the manuscript 

 geological map of England and Wales of 1801 appear to have been 

 very similar to those used in Smith's later engraved maps. 



There is nothing in the way of an index of colours attached to 

 this first geological map of England and Wales, but, by reference 

 to the author's later publications, it is not difficult to determine what 

 the seve;i'al bands of colour are intended to indicate. The formations 

 of which the outcrops are represented range from the Chalk to the 

 Old Red Sandstone, the colours employed being eight in number, 

 though a number of other signs, indicating collieries, mines, and 

 slate-quarries, adds much to the valuable information supplied by 

 this remarkable map. 



The strata represented are, in descending order, as follows : — 



1. Chalk (green). 



2. " Sand of the Portland Eock," with which is confounded (as 



in later maps) the Carstone of Norfolk (purple). 



3. Oxford Clay ("Church Clay" of Smith) (grey). 



4. Oolite. The outcrop represented is that of the Great Oolite of 



the Bath area, and of the Inferior Oolite both south and north 

 of that area (yellow). 



5. Lias (dull blue). 



6. Trias and Permian (" Eed Marl " of Smith) (Ught red). 



