246 MESSRS. R. H. RASIALL AND J. ROMANES ON [^- u g' x 9°9i 



16. On the Boulders of the Cambridge Drift : their Distribution 

 and Origin. By Bobert Heron Bastall, M.A., P.G.S., and 

 James Bomanes, B.A. (Bead April 28th, 1909.) 



Contents. 



Page 



I. Introduction 246 



II. Summary of Previous Literature 246 



III. Method of Investigation 247 



IV. Short Account of the Glacial Drift of Cambridgeshire 249 



V. Details of each District in Separate Sections (with Map) ... 251 



VI. General Remarks 259 



VII. Summary and Conclusions 260 



I. Introduction. 



The origin and distribution of the boulders of the Glacial Drift 

 of Cambridgeshire and the adjoining counties is a subject of great 

 interest on which hitherto little work has been done. Although 

 much has been written on the Glacial deposits of this district as a 

 whole, little attempt has been made to examine in detail the types 

 of rock represented in the Boulder-Clay and to trace them to their 

 sources. During the last seven or eight years a large amount of 

 material has been collected, both by the members of the Sedgwick 

 Club and by other independent workers. A brief account of soma 

 of the results obtained up to that time was given by Mr. Fearnsides 

 in the official hand-book compiled for the Cambridge meeting of 

 the British Association in 1904, and a short paper entitled ' On 

 Boulders from the Cambridge Drift, collected by the Sedgwick 

 Club ' * was published in the same year by one of the present 

 authors. Since that date much new material has been collected, and 

 the whole has now come into our hands. The additional evidence 

 thus made available, shows that the conclusions set forth in the 

 previous publications can be considerably extended. 



The total number of boulders collected now amounts to many 

 hundreds ; and, as naturally would be expected, a great number of 

 them, perhaps the majority, are of uncertain origin, since it is clear 

 that the field of derivation is a very wide one. However, a large 

 number of rock-types have been identified, either provisionally or 

 with certainty ; while in the case of many more the identification 

 is highly probable. 



II. Summary oe Brevious Literature. 



The following list does not claim to be a complete bibliography 

 of the subject. It includes only a few of the more important 



1 Geol. Mag. 1904, p. 542. 



