116 REPORT— 1888. 



striated with deep grooves of almost parallel striae on two sides, and 

 many of tlie boulders of clunch and hard chalk are also clearly striated, 

 but the direction of the strife is very irregular. Among the whitened 

 flints also there are some exceedingly good examples of cross-striation. 

 Striffi are not often to be seen on the hard sandstones and the igneous 

 boulders, though there are a few good examples of it ; but most of these 

 boulders are quite smoothed and some are highly polished. Of the 

 igneous rocks some are so much weathered that the outer surface comes 

 oflf in successive coats, like a thick-coated onion, whereas others, and 

 especially the larger boulders, are perfectly unweathered and have a very 

 dark almost black polished surface, so hard and rounded that it is often 

 exceedingly ditBcult to get a hand specimen. They consist mainly of 

 fine-grained dolerites and microcrystalline basalts, with a fair sprinkling 

 of quartz-porphyrites, mostly containing tourmaline, felspar-porphyrites, 

 and hornblende schists and gneiss. Amid the almost complete absence of 

 boulders, or even pebbles, of granite or syenite, one boulder which I have 

 lately found is remarkable : it is a large boulder of a pinkish grey syenite, 

 of very distinct rather coarse texture and containing abundant orthoclase, 

 not much quartz, not a great amount of hornblende, and a little biotite. 

 Dr. A. Geikie has seen a hand specimen and microscopic section of it, 

 and he informs me that he cannot identify it with any British rock 

 known to him, and that Dr. Hatch cannot find any specimen at tho 

 Jermyn Street Museum really like it. I have also been informed by Dr. 

 Crosskey that nothing like it has been found among the erratics in the 

 Midlands, though a considerable number of boulders of syenite have been 

 found there. I have sent a hand specimen to Christiania to see if it can 

 be identified there. In a gravel pit on the high ground near Felstead I 

 dug out a remarkable boulder of quartz and tourmaline, almost round and 

 highly polished and striped with parallel bands of black and yellow, and 

 among tho specimens of erratics in the Midlands which Dr. Crosskey has 

 collected I found one that was identical with it. Of the boulders of 

 dolerite it is somewhat remarkable that, although smaller boulders occur 

 in all directions, yet all the larger boulders which I have at present 

 found lie north of the old Roman road which runs through Braintreo 

 and Dunmow ; as many as six large boulders are lying within a com- 

 paratively small area, one of these being distinctly columnar in form and 

 one being very clearly striated. As regards the dolerites generally I 

 have already stated (' Q. J. G. S.' August 1887, p. 35G) that some of then> 

 are strikingly similar in specific gravity, in general appearance, and in 

 some remarkable microscopic points with some specimens of dolerites 

 sent me from Sweden, and that others are almost identical with the rocks 

 of the Whin Sill in the north of England, though these also might well 

 be Scandinavian boulders, as I understand that the Hunneberg rocks- 

 have been shown to be of the Whin Sill type. But one of the most 

 remarkable of the boulders which I have as yet found was exposed in 

 digging the foundations of a new house at Booking Place, Braintree 

 (Mr. S. Courtauld) : it was found at a depth of eight feet from the 

 surface and measures 22 x 18 x 11 in. ; it is rounded and smoothed, 

 roughly triangular in shape, and has two more or less flat surfaces : both 

 of these surfaces are very distinctly grooved with irregular strife. I sent 

 a hand specimen and a miscroscopic section to Professor Bonney, who 

 kindly examined both and wrote as follows : ' The rock is a curious one 

 and must have come a long distance. ... So far as I can venture to 



