Reviews — Delesse's Lithologle du Fond des Mers. 77 



dation are concerned — wind, rain, rivers, glaciers, and breakers, etc. 

 — the ordinary views are clearly defined by him, and much valuable 

 tabulated detail is given respecting the velocity, sediment, etc., of 

 the principal rivers of France, in a manner which makes one wish 

 that something of the kind were done for Great Britain. 



M. Delesse's Chapter viii. however is a distinct contribution to 

 submarine geology, and deserves to be given in his own words. It 

 treats of the internal agents, and forms a clear expose of the views 

 now held by the leading French geologists on an important branch 

 of Dynamical Geology :— 



" These," he says, " can produce equally effects either of erosion 

 or of transport ; more often even they bring into the sea and into 

 sea-deposits mineral substances coming from the interior of the globe. 

 These agents are subterranean waters, eruptions, and dislocations.^ 

 "I. — Subterranean Waters. 



The waters which penetrate into the earth obey the laws of 

 gravity, descend slowly through the pores or interstices of the rocks, 

 and end by re-uniting into subterranean sheets. Hidden from our 

 eyes, they flow into the beds of rivers and into sea-basins ; sometimes 

 they fall into them at their upper portions, sometimes low down. 



The infiltrations of subterranean sheets of water into the basin of 

 the ocean take place incessantly, and on an immense scale ; they even 

 represent a very considerable proportion of the meteoric waters 

 which fall on the emerged portion of our globe. Moreover, they 

 take place, not only towards the ujjper level of the ocean, but also 

 along its sides and down to the lowest depths. 



Now, the subterranean sheets of water are charged with mineral 

 substances, which are furnished by the rocks through which they 

 pass, and these they bring to the ocean. In particular do they bring 

 silica and carbonate of lime, which the sponges and molluscs after- 

 wards concentrate in deposits. 



Sometimes they are sufficiently charged with carbonate of lime to 

 produce calcareous tuffs, like those which are now being formed at 

 the bottom of rivers and on the sea-coasts. 



The mineral substances become, besides, more abundant in the 

 underground sheets of water according as the latter contain more 

 carbonic acid, as they have a higher temperature, and consequently 

 as they reach a greater depth. The underground sheets of water 

 therefore introduce mineral substances into the ocean, and they must 

 play a rather important part in the formation of marine deposits. 



Independently of these submarine infiltrations, produced by waters 

 falling on the surface of the globe, and penetrating its crust, there 

 are others in existence which are due to mineral waters of an erup- 

 tive nature, and disengaging themselves on the contrary from its 

 interior. 



These last are local ; for they can only come to the day through 

 the fissures of the earth's crust ; but their temperature is high, so 

 that they hold a large proportion of substances in solution. They 



^ The subject has since been enlarged on by M. Daubree iu a paper noticed in the 

 Geological Magazine, 1873, Vol. X. p. 472. 



