ey^O 



Revietcs — R. LydeliJcers Catalogue of Fossil Mammalia. 321 



American river is lowered at the rate of about one foot in 6000 

 years, but Mr. Reade observes that this rate has been calculated from 

 the removal of sediment alone ; and if we add to the matter removed 

 mechanically that in solution, it will raise the rate to one foot in 

 4500 years. Of course much denudation is subterranean, and 

 especially chemical denudation, but no doubt such losses lead 

 eventually to a lowering of the ground by subsidence of material 

 into fissures and cavities. 



It is interesting to learn from the analysis of the Mississippi water 

 that more than 23 millions of tons of silica are poured into the sea 

 annually by this river, apart from sedimentary detritus. 



Mr. Reade gives some particulars of the chemical constituents of 

 the River Plate, but the amount of solid matter carried away in 

 suspension by that river is not known. Particulars relating to the 

 river St. Lawrence and the Amazons are also given. 



With regard to the dispersion of river-sediments over the ocean 

 bottom, Mr. Reade observes that while an admixture of sea- water 

 with turbid freshwater tends to hasten the precipitation of the solid 

 matters, yet it is very probable that the extremely divided solid 

 matter will be carried far and wide by oceanic currents before it can 

 settle to the bottom. Hence, he thinks, much of the argillaceous 

 matter or " Red Clay " is more likely to be the " dust of continents " 

 than volcanic debris, although no doubt volcanic materials are 

 largely commingled with it; and he objects to the view that the 

 Red Clays furnish in any way a proof of the permanence of oceanic 

 areas. Much of the mineral matter carried to sea in solution is used 

 up by pelagic animals, and thus eventually finds its way to the 

 ocean-bottom ; and had nature no means of redistributing these 

 oceanic deposits by upheaval into land, the constitution of the rocks 

 of the globe would be undergoing a gradual alteration. 



II. — Catalogue of the Fossil Mammalia in the British Museum 

 (Natural History). Part I. Containing the Orders Primates, 

 Cheiroptera, Insectivora, Carnivora, and Rodentia. By Richard 

 Lydekker, B.A., F.G.S., etc. 8vo. pp. xxx. and 268. Illus- 

 trated by 33 Woodcuts. (London : Printed for the Trustees, 

 1885.) 



IN the first half of the present century, when the interest attaching 

 to Fossil remains was mainly concentrated in the determinatioQ 

 of their geological locality and exact stratigraphical position, but 

 few naturalists at that time sought to correlate living animals and 

 plants with the long line of ancestral forms whose remains occur 

 in the various stratified rocks beneath our feet. 



Thanks, however, to our great master, Lyell, geologists have been 

 taught to recognize the fact, that the same agents which are in 

 action to-day. Rain, Rivers and Sea, Frost and Snow, Cold and Heat, 

 have been in operation ever since dry land appeared above the 

 surface of the waters, and that instead of invoking one cataclysm 

 after another, it was more reasonable to conceive an ever-recurring 

 cycle of geological events, slowly succeeding each other, yet surely 



DECADE III. VOL. II. — NO. YII. 21 



