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POPULAR SCIENCE REVIEW. 
drew attention to tlie evidence of tlie deposition of secondary quartz upon the 
original grains, so as to continue their crystal structure, which sometimes 
exhibits externally a crystal form. This is frequently observable in sand- 
stones of Carboniferous, Permian, and Triassic age. Felspar grains are not 
unfrequently present, with scales of mica and minute chlorite and epidote. 
The author then considered the effect of flowing water upon transported 
particles of sand or gravel. It results from his investigations that frag- 
ments of quartz or schorl less than ■£/' in diameter retain their angularity 
for a very long period indeed, remaining, under ordinary circumstances, un- 
rounded ; but they are much more rapidly rounded by the action of wind. 
It is thus probable that rounded grains of this kind in some of the older 
rocks, as, for example, certain of the Triassic sandstones, may be the result 
of AEolian action. 
Abnormal Geological Deposits in the Bristol District. — On the 17th 
November, Mr. Charles Moore read a paper on certain curious deposits in 
the country about Bristol, which may be regarded as a continuation of 
researches published by him some thirteen years ago upon similar pheno^ 
mena in the districts of Somersetshire and South Wales. 
The author remarked that the Frome district shows numerous un- 
conformable secondary deposits and 1 vein-fissures ’ resting upon or passing 
down through the Carboniferous Limestone, as described in his former 
paper {Quart. Journ. Geol. Soc. vol. xxii. p. 449). He gave some further 
particulars as to these deposits, and especially described the occurrence of 
Post-pliocene, Liassic, and Bhaetic deposits in the Microlestes-quaxTy near 
Shepton Mallet. Here the lower part of a fissure is filled with a brown 
marl, containing crystals of carbonate of lime, and numerous remains of 
Arvicolee, Frogs, Birds, and Fishes. The jaws of Arvicolee were very 
abundant. 
He then proceeded to describe the occurrence of similar phenomena in 
the Bristol area, as at Durdham and Clifton Downs, in the gorge of the Avon 
at Clifton, at Ashton and Westbury-on-Trym, in the Yate rock, in Nettle- 
bury quarry, at Clevedon, and on the Thornbury railway. He noticed the 
occurrence in the infillings of fissures traversing the Carboniferous Lime- 
stone of these localities of fossil remains belonging to various geological 
ages ; and he especially called attention to the presence in different deposits 
of an immense number of small tubular bodies of doubtful origin, for which, 
should they prove to be of organic nature, he proposed the name oiTubutella 
ambigua. By different authorities these little bodies have been assimilated 
to Serpulae (Filograna), insect-tubes, and the casts of the fine roots of plants. 
With regard to the age of the fissure-deposits, the author remarked that 
although in some fissures the infilling shows a mixture of organisms, in most 
cases each 1 vein ’ appears to have an individuality of its own, and thus the 
veins represent intervals of geological time clearly distinct from one 
another, different fissures showing infillings of Alluvium, Oolite, Lias, Rhsetic, 
and Keuper beds. The presence of his Tubutella he considered to indicate 
fresh-water conditions. 
The author also referred to the discovery of Thecodontosaurus and 
Falceosaurus many years ago at the edge of Durdham Down, and discussed 
the age of the deposit containing them, which w r as originally supposed to be 
I ! 
