E. A. Martin — Foreign Boulders in the Chalk. 169 



As far as I can see, the only stratigraphical difficulty which 

 presents itself is the occurrence of the Pendleside limestones at 

 such a distance from the main mass as 2500 feet. But it appears 

 to be very local in its development, and it is certainly not to be 

 traced to any distance except perhaps to the north-east, while the 

 great mass of shale itself thins out very rapidly in the same 

 direction. The Pendle Hill and Longridge sections are extremely 

 valuable, for they both exhibit a complete sequence from Coal- 

 measures to the Carboniferous Limestone. It must also be 

 remembered that the whole of the Millstone Grit Series is really 

 a very local deposit, only appearing in force in South Yorkshire, in 

 Lancashire and Derbyshire, rapidly thinning out both to the north 

 and south. 



(To be concluded in our next Number.) 



VI. — Foreign Boulders in the Chalk. 

 By Edward A. Martin, F.G.S. 



THE recent find by Mr. Stebbing, F.G.S. , of two large boulders 

 of granite in the Middle Chalk of Betchworth (Surrey), has 

 called to mind the various discoveries of boulders which had 

 previously been made in the same marine formation by other 

 observers. 



I am not aware whether the discovery of the so-called Purley 

 syenite boulder (from the Haling Pit, South Croydon) has ever 

 been considered in connection with that remarkable boulder which 

 was dredged up by the " Challenger " off Halifax, This, too, was 

 of syenite, and weighed no less than o cwt., and was brought up 

 from a bottom of grey mud contaiuiiig many foraminifera. Whatever 

 could be said on behalf of some of the boulders from the Chalk 

 having been conveyed by floating seaweed, or the roots of trees, the 

 probabilities are all in favour of this block having been transported 

 by ice, in a sea where so many icebergs are found at certain seasons 

 of the year. And this without the necessity of inventing a special 

 Glacial Epoch. We may argue from the one to the other, and 

 without any very great stretch of imagination see the work of an 

 occasional iceberg in the occasional occurrence of a boulder of 

 foreign material in the Chalk. 



The great Purley or Haling boulder, the boulder from the 

 Gay ton Pit, Norfolk, and others, are all thoroughly rounded. From 

 this reasonably follows that they must have suffered much before 

 being imbedded in the iceberg, perhaps on that shore which existed 

 around those portions, compai'atively small, of modern Europe, 

 which even then were raised high and dry above the Chalk sea. 

 The Betchworth boulders are not nearly so rounded. Added to 

 this, fragments of Spondyhis and Serpulcs are still attached thereto. 

 Icebergs take a long time to melt, and I think there is just as much 

 likelihood of Serpulcs becoming attached to a submerged block of 

 granite as barnacles to a ship's bottom. At the same time the 

 presence of Serpidce seems to show that there could not have been 

 a " Glacial epoch." 



