304 



THE GEOLOGIST. 



superseded by others essentially different, a new region or zone must be 

 said to begin. This constancy of character among the organic inhabitants 

 within determined vertical or horizontal limits, could not take place if cer- 

 tain external circumstances were not vital conditions for a great many or- 

 ganic beings, whose existence can only be continued and propagated under 

 a determinate combination of physical agencies or whose power of natural 

 selection and its results (to speak in the sense of Dr. Darwin's hypothesis) 

 is essentially dependent on these agencies. At all events, organic beings 

 consociate in those spaces within which they find the means of satisfying 

 their special conditions of existence. These conditions for marine organ- 

 isms are : — the nature of the sea-bottom, the temperature of the sea- 

 water, its saltness, its permeability to light, its pressure, undulations, cur- 

 rents, and tides ; just the objects to be treated in a physical geography of 

 the sea. The distribution of marine organic life can, of course, only be 

 thoroughly understood by the aid of hydrography. This branch of science 

 may however turn mto profit the results of organographic investigations, as 

 being indicative of certain hydrographical conditions, which, without them, 

 could only be stated by means of a long series of observations, and must 

 consequently, in certain cases, remain far behind the special purposes to 

 be attained by them. 



Professor Lorenz, in the course of his investigations, took great care 

 never to lose sight of the intimate connection existing between hydrogra- 

 phy and organography. The introductory part of his book begins with 

 an exposition of the mode of action of each single agent. He proves the 

 depth, generally considered, according to Edward Forbes, to be in itself a 

 condition of distribution, to act only as a combination of other factors. 

 In the following chapters the author discusses each of the above-named 

 factors, in itself and in its connection with others, basing his comments on 

 his own numerous observations in the Quarnero. 



The factors depending on the solid basin containing the sea and the at- 

 mosphere in immediate contact with its surface, — that is, the geographical, 

 bathy metrical, geological, and meteorological conditions, — are first brought 

 under discussion. A very instructive map, partly of chromotypic execu- 

 tion, serves to illustrate the variations of depth and of the nature of the 

 bottom, both in open sea and along the shores. 



In the chapter on climatic conditions, in many respects depending on 

 those of the neighbouring continental regions, the author expresses his re- 

 markable views on the mutual connection between wind and weather, 

 shows the origin of certain winds regulating the march of weather, and 

 derives from their nature a series of typical atmospheric conditions (Bora, 

 Scirocco, Maestral, Tramontana, and Provenza weather), with their pro- 

 gnostics, courses, distributions according to seasons, etc. The explanation 

 given by him of the " habitual Bora," with its characteristic blasts of 

 wind (Repoli), is particularly of scientific and practical interest. Accord- 

 ing to Dr. Lorenz's observations, the north-east wind passing over the 

 high and steep slopes of the Karst is innoxious in itself, whether it comes 

 from inland regions, or originates over the plateau of the Karst by local 

 compensation between two atmospheric currents different in density or 

 temperature. It acquires only a dangerous intensity whenever a scirocco, 

 blowing in opposite direction to or a little above it, presses it more or less 

 violently against the plateau of the Karst and forces it into a narrower 

 space. Besides this normal Bora, two other varieties of it, of non-danger- 

 ous nature and of different origin, are known to exist. 



The waters of the Quarnero contain salt in an average proportion of 

 3*76 per cent., their density is = 1*023 at the surface and:=r0275 at 



