Vol. 65.] THE BOULDERS OF THE CAMBRIDGE DRIFT. 255 



now known to exist among the Carboniferous rocks of East Lothian. 

 The common pink granulitic granite is represented, and there is a 

 considerable number of metamorphic rocks, which it is noteworthy 

 are schistose rather than gneissose ; whereas, in the immediate 

 neighbourhood of Cambridge, gneisses are far more common than 

 schists. 



(3) Lords Bridge, Barton, and Comberton : 93 specimens. 



In this area a large number of specimens have been found. 

 There are two rhomb-porphyries of the vesicular volcanic facies, one 

 from a mile north-west of Barton Church and one from Comberton. 

 Besides these the Scandinavian province is represented by a soda- 

 granite, an augite-syenite, and another alkali-syenite with a blue 

 soda-amphibole and abundant perthite. Three examples of a coarse 

 felspathic grit are referred to the Sparagrnite of Norway. The 

 neighbourhood of Lords Bridge is the locality in which porphyry x 

 was originally discovered, and eleven fine examples were obtained, 

 some fairly large. With these are associated a good example of the 

 Forfarshire porphyry. No less than eighteen boulders, including 

 an analcime-dolerite, seem to belong to the Forth Valley or North 

 Berwick type, and Cheviot lavas are common. Among other types 

 represented are greywackes, possibly Silurian, pink granulites (8), 

 dolerites (12), and numerous specimens of various metamorphic 

 rocks. 



(4) Barrington and Foxton : 49 specimens. 



The collection from Barrington is not large, but it includes 

 several specimens collected by Prof. Hughes, Mr. Keeping, and 

 others from the Barrington gravels. A very fine rhomb-porphyry 

 collected by Mr. Keeping bears date 1884, but it was apparently 

 not identified at that time. There are moreover a nordmarkite, 

 two nordmarkite-porphyries, five soda-granites, and one segirine- 

 granite ; also an especially fine specimen of Sparagmite, which 

 bears a very strong resemblance to some varieties of the Torridon 

 Sandstone. There is one good porphyry x. 



One of the most interesting specimens from Barrington is a 

 porphyritic rock, with large pale pink felspars and quartz set in a 

 dark brown ground-mass. Our special attention was first directed 

 to this rock by Dr. Bonney, who remarked on its similarity to a 

 specimen of the Buchan Ness quartz-porphyry in his collection. 

 It has since been submitted to Mr. B. Campbell, who confirms the 

 identification in this and other eases to be mentioned later. 



Seven examples of Cheviot dykes and lavas are included, also 

 six pink granulitic granites. A rather remarkable feature is the 

 rarity or apparent absence of basic igneous rocks, which are so 

 common elsewhere : the only representatives of this group are one 

 specimen each of olivine-basalt and gabbro. Metamorphic rocks 

 also appear to be rare. 



