188 



HARDWICKE'S SCIENCE -GOSSIP. 



Bariiet and round about, but the gravel varies 

 in different localities in its structure and compo- 

 sition, so much so as to lead some geologists to 

 make two divisions ; namely, pebble gravel and 

 middle glacial : the whole of it is, however, older 

 than the bouldcr-clay. The middle glacial gravel 

 and sand underlie the boulder-clay of Piuchley and 

 Whetstone, and contain fragments of many rocks, of 

 ■which flint, quartz, and quartzite are predominant, 

 the flint being sub-angular and rounded; the gravel 

 also contains numerous rolled fossils from many 

 different geological formations. The pebble gravel 

 is characterized by the very rounded nature of its 

 materials, and is made up almost entirely of pebbles 

 of quartz and flint. It caps the high grounds at 

 Barnet and other places north of Finchley. I am 

 not aware that any derived fossils have been found 

 in it, and it would therefore be interesting if your 

 correspondent found some. 3. The boulder-clay 

 may be recognized by the occurrence in it of 

 numerous pellets and boulders of chalk, which often 

 give it a whitish appearance. It also contains 

 unworn flints, and rocks and fossils from a number 

 of geological formations. Mr. Wetherell, of High- 

 gate, has made an extensive collection of British 

 fossils from the boulder-clay and gravel of Finchley 

 and Muswell Hill. It may be studied in the railway- 

 cuttings near Church End, Einchley, and it is also 

 scattered here and there over the country to the 

 north. In regard to publications referring to the 

 district, I may mention Mr. Henry Walker's pam- 

 phlet on the " Glacial Drift of Muswell Hill and 

 Einchley," 1874^ (price 6d.) ; also the Geological Sur- 

 vey Map, sheet 7, showing drifts, which in the neigh- 

 bourhood of Barnet were surveyed by Mr. P. J. 

 Bennett and myself, and Mr. Whitaker's "Memoir 

 on the Geology of the Loudon Basin." The two latter 

 publications, albeit rather expensive, would be 

 useful in long excursions, when the chalk and 

 Beading beds displayed at South Mims and Northaw 

 might be ex&mmed.— Horace B. Woodtcard, Geo- 

 logical Survey of England and IFales. 



Fossil Oyster-bed.— A fossil oyster-bed has 

 recently been discovered near Croydon ; it extends 

 over a considerable ares, and lies about ten feet 

 below the surface, in a stratum of clay, sandy loam, 

 and pebbly gravel, locally known as pea gravel ; the 

 bed is a friable mass of shells and is only about 

 seven to fourteen inches in thickness : some casts 

 of oysters are very perfect, and several other species 

 of shells occur, but not in such good condition. 

 I have heard that a lobster has also been found in 

 the same bed. — E. Lovett. 



Geology of Barnet. — K. Brierly should get, or 

 see sheet 7, of the Geological Survey Map, the last 

 edition (with the drifts shown). The Memoir on 

 that sheet is out of print, but the greater part of it 



is absorbed in a larger Survey Memoir " on the 

 London Basin" (1872). A popular account of the 

 Glacial Drift south of Barnet has been given by 

 Mr. H. Walker, in a sixpenny pamphlet entitled 

 "The Glacial Drift of Muswell Hill and Finchley" 

 (1874), which K. B. would do well to get.— /T. 

 Wliitaker, Geol. Survey. 



Organisms in Carboniferous Flint ok 

 Chert. — In a piece of flint or " chert " derived from 

 the Yoredale series of the Carboniferous system, I 

 have met with some interesting microscopic organ- 



Fig. 123. Fraement of supposed 

 foraminifera in chert. 



Fig. 124. Longitudinal sec- 

 tion of ditto. 



Fig. 125. Transverse section of ditto, all x 40. 



isms, the nature of which I should lie very glad 

 to know. The two fragments seem to be portions of 

 foraminifera, and possibly the others also. Perhaps 

 some of the readers of Science-Gossip may be able 

 to throw light upon this difficulty.—/. S. Tute. 



NOTES AND QUERIES. 



Variety of LniE Ha"wks. — " W. L. S.," on page 

 135, says he found in his breeding-cage a strange 

 variety of the Lime Hawk, and then gives a descrip- 

 tion of the insect. From this description, I should 

 most certainly conclude that the insect is not a 

 Lime Hawk. Would Mr. Sergeant kindly inform 

 me, through the Science-Gossip, whether the cater- 

 pillar and the chrysalid were the same as "limes" 

 usually are. I think it is either entirely a new 



