314 J. W. Davis — Erratic Boulders of the C alder Valley. 



gravels, sand, and boulders. At Wakefield wells have been dug to 

 a depth of twenty -eight and thirty feet, and at Thornhill and Dews- 

 bury excavations have proved the deposits to be between forty and 

 fifty feet in depth. Still further up the valley, from Elland to 

 Sowerby Bridge, the gravels and boulders occur in some force, and 

 are at least twelve to sixteen feet deep. The valley nearer its source 

 than the latter locality is almost devoid of gravels ; and where they 

 do occur, as at Mytholmroyd, the travelled boulders are rare, or 

 altogether absent. From Sowerby Bridge southwards the drift or 

 gravel is composed of rounded pebbles and sand ; these, near the 

 surface, are almost entirely derived from the local sandstones 

 and Galliards ; in the lower strata boulders of granite, trap, and 

 syenite become gradually more frequent, until in the lowest parts they 

 attain a great preponderance, and rocks of local origin are almost as 

 rarely found as crystalline ones were in the upper part of the series. 

 In the sections low down the valley, the boulders are frequently of 

 considerable size, and at Dewsbury masses of granite and limestone 

 were found near the base of the section exceeding a foot in diameter ; 

 they were in all cases well rounded and quite devoid of scratches. 

 The following section of a well sunk at Dewsbury may be taken as 

 an average example : — 



1. Earth and sandy subsoil 7ft. 6in. 



2. Boulders, consisting in the upper part of sandstone with 



a slight intermixture of granite, etc., gradually 



merging into 24ft. Oin. 



3. Boulders, almost entirely of crystalline rocks not 



occurring in the district in si tu 6ft. Oin. 



4. Clay with sand and boulders 5ft. Oin. 



Carboniferous sandstone 



A remarkable circumstance is the occurrence in the lower beds of 

 rounded masses of flint, along with granite, syenite, and trap 

 rocks, the latter having been identified with their parent rocks in 

 Westmoreland and Cumberland, and even in some few instances with 

 rocks of Scotch derivation, whilst the flints are similar to those 

 occurring in the Chalk in the eastern parts of the Yorkshire Wolds. 

 There is an entire absence of shells of Mollusca, but near Thornhill 

 the trunks of several trees have been found at a few feet below the 

 surface of the gravel beds, presenting an appearance indicating that 

 they grew at no great distance from the position they occupied when 

 found. A more detailed description may be found in the Proceedings 

 of the Yorkshire Geological and Polytechnic Society for the year 

 1875, page 93. 1 



In addition to the boulders already enumerated, Shap Fell granite 

 has been found in the district south-east of Wakefield. Though 

 comparatively rare, they are found sufficiently often to form a 

 characteristic boulder ; the large masses of pink felspar being a very 

 important constituent, which renders their identification unmistakable. 

 The occurrence of this granite, as will be shown hereafter, throws a 

 most important light on the origin of the gravels. 



1 See also a paper by J. Travis Clay, Esq., of Rastrick, Proc. Geol. and Polyt. 

 Soc. of the West Biding of Yorkshire, vol. i. p. 201 (1841). 



