132 Reviews — P. N. Veni/ukov's Silurian of Podolia. 



percentage of 8oda in sedimentary rocks is only 1'47 (p. 44), it is 

 obvious that a much higher rate of denudation would be required 

 to yield annually by decomposition of such rocks the amount of 

 sodium carried down by the rivers. The conclusion will be that, 

 if one foot denuded in 6,000 years is near the truth, the sodium in 

 the rivers must have some further source than the soda which forms 

 a mineral constituent of the surface rocks, and that this additional 

 soda is probably derived, as already suggested, from " fossil " sea- 

 water. Ought not also some allowance to be made for the soda 

 introduced into rivers by human agency ? 



The style of the paper leaves here and there a little to be desired 

 in respect of clearness; for instance (p. 47), "We can apply to the mean 

 analysis of the sedimentaries on the one hand, and to that of the original 

 crust on the other, to arrive at a rough estimate of the loss of entire 

 rock by solution in the process of formation of the former." Again 

 (p. 46), " We accept one mile deep of these [detrital sediments] on 

 the land, and confining ourselves to purely detrital siliceous 

 sediments, assume that as much as 10 per cent, of what is on the 

 land is in the sea [!], or say a total of 1*1 mile deep over the 

 land area." 



In this important essay Professor Joly has opened up an entirely 

 new line for the investigation of geological time. It is too soon to 

 pronounce whether his numerical estimate is fully to be relied upon, 

 until it has been a little while before the scientific world. His 

 period of between 80 and 90 million years will perhaps satisfy 

 geologists as being sufficient. The leading physicists, on the other 

 hand, are disposed to grant us a good deal less time. 



0. FiSHEE. 



Harlton, Cambkidge. 

 January 22, 1900. 



II. — The Fauna of the Silurian of Podolia. 



Fauna siluriiskikh otlozhenii podol'skoi gubei'nil. Die Fauna der 

 Silurischen Ablagerungen des gouvernements Podolieu. By 

 P. N. Venyukov (Wenjukow). Mater. Geol. Kusslands, XIX, 

 pp. 21-266, pis. i-ix ; November, 1S99. 



PODOLIA, which lies to the south-west of Kiev, is bounded on 

 the south by the Dniester and on the west by Galicia, and is 

 drained by a river beloved of every schoolboy — the Bug. The 

 Silurian rocks are all in the south-west of the province, adjoining 

 the similar formations of Galicia. The present work by Professor 

 Venyukov of Kiev describes the fauna of these rocks, unfortunately 

 for us, in Eussian ; but the broad results may be gathered from the 

 short abstract in German, while the new species, of which there are 

 not a few among corals, brachiopods, molluscs, and ostracods, may to 

 some extent be identified from the plates. The Silurian geologist 

 will certainly have to read the abstract, and the specialist in 

 palasontology must get the Eussian descriptions translated for him. 

 Here we give only the main conclusions. 



