SCIENTIFIC SUMMARY. 
95 
present level of the sea. The close coincidence in height is remarkable, 
and if these elevations at such distant points were contemporary, it implies 
a uniform amount of oscillation over a very large proportion of the Medi- 
terranean area. The raised coast deposits at Tangier and Cadiz may have 
been connected with an independent oscillation of greater antiquity than 
the 25 feet rise, hut yet more recent than that which submerged and re- 
elevated Gibraltar at least 700 feet. 
British Fossil Crustacea. — Mr. H. Woodward, we are glad to see, con- 
tinues his account of British Fossil Crustacea. In his fourth Report to the 
British Association, he described, among other Crustacea, two species be- 
longing to the genus Cyclus , one of which still remains unique. Since that 
date, he has, by the kindness of Professor T. Rupert Jones, F.G.S., received 
a number of specimens of this genus, collected by Professor Harkness, 
F.R.S. ; Mr. Joseph Wright, of Belfast ; and Mr. J. H. Burrow, of Settle, 
Yorkshire ; from the carboniferous limestone, which he describes partly 
in the last number of the u Geological Magazine ” and figures in an interesting 
plate accompanying his paper. 
The Motion of a Glacier . — This important question lies for discussion 
between Canon Moseley and Mr. Croll, F.R.S. E. Mr. Croll has communi- 
cated some remarks on the subject to the 11 Philosophical Magazine ” for 
September. To him there seems to be but one explanation of glacier 
movement, namely, that the motion of the glacier is molecular. His con- 
cluding remarks are as follows : — The ice descends molecule by molecule. 
The ice of a glacier is in the hard, crystalline state, but it does not descend 
in this state. Gravitation is a constantly acting force ; if a particle of the 
ice lose its shearing-force, though but for the moment, it will descend by 
its weight alone. But a particle of the ice will lose its shearing-force for a 
moment if the particle loses its crystalline state for the moment. The 
passage of heat through ice, whether by conduction or by radiation, in all 
probability is a molecular process — that is, the form of energy termed heat 
is transmitted from molecule to molecule of the ice. But at the moment 
that it is in possession of the passing energy, is the molecule in the crystal- 
line or icy state ? If we assume that it is not, but that in becoming 
possessed of the energy it loses its crystalline form, and for the moment 
becomes water, all our difficulties regarding the cause of the motion of 
glaciers are removed. We know that the ice of a glacier, in the mass, 
cannot become possessed of energy in the form of heat without becoming 
fluid ; may not the same thing hold true of the ice-particle P 
Sir R. Murchison's Report on the Geological Survey and the Museum of Prac- 
tical Geology . — This has been published, and will interest the geologist who 
is desirous of knowing what work the year 1869 has shown in these respects. 
A total area 2,634f square miles was surveyed during the year. This was 
in England. In Scotland, Mr. A. Geikie reports 111 square miles as being 
shown. In Ireland 797 square miles have been surveyed. In regard to the 
museum Professor Huxley reports several valuable additions which have 
been made during the year. The maps, mining office, and laboratory, are 
also most favourably reported upon. 
Mr. Forbes' Lecture on Volcanoes . — In the u Geological Magazine " for 
November, Mr. D. Forbes, F.R.S., replies to the remarks of Mr. Poulett 
