176 EFFECTS OF FORESTS ON SPRINGS. 



Agricultural districts." In this the author, after having in an Intro- 

 duction shown the great importance of the subject, invites his 

 colleagues as well as other naturalists to examine his book, and 

 appeals for the support of the Government in favour of his pro- 

 positions, especially those departments of the Government which ai-e 

 more specially occupied with the care and defence of the economical 

 interests of the public ; after which he treats, in the first place, of the 

 diminution of water in the rivers and streams, and consequently the 

 diminution in the out-flow. He proceeds upon personal observations 

 during a period of forty years, made on the Austro-Hungarian great 

 rivers and streams, with relation to the conditions of their out-flow, 

 and he comes to the conclusion that the volume of water at present 

 discharged has decreased considerably during a series of years. 



Corresponding facts have been attested also by others, and judging 

 from these they have given their opinion that the volume of water 

 discharged by many streams appears to be diminishing. But the 

 correctness of this conclusion has been disputed, and the author 

 discusses the obsei-vations which have been adduced against the views 

 adopted by him, as well as those upon which his conclusions were 

 based. 



The author proceeds on data supplied in the Second Part of the 

 Allegmeine Lander und Volkerk^mde, by Berghaus, in regard to the 

 depth of water in the Rhine at Emmerich, of the Elbe at Magdeburg, 

 and of the Oder at Kiistrain, according to which the average and 

 lower depths of water have experienced a diminution by no means 

 inconsiderable, while the floods of greatest depth present, on the 

 other hand, apparently an increase both in frequency of occurrence 

 and in magnitude. 



Dr Berghaus became convinced through an examination of the 

 tables of the depth of water in the Elbe and the Oder that on the 

 main streams of both the flow or delivery have been considerably 

 diminished ; and he expressed a fear that these two rivers of Germany 

 were threatening to disappear from the number of navigable rivers, 

 which would be the case if the reduction in the depth of water should 

 go on at the same rate at which it had proved to be diminishing since 

 the year 1781. 



Herr Wex, by long-continued observations and studies, had come to 

 the same conclusion as Berghaus, and he maintains against objections 

 brought forward on difi^erent sides the opinion that there has been a 

 progressive diminution in the quantity of water in these rivers, and 

 not less really so in the Vistula and the Danube. 



