RAPPORT OP M. OOLMANN. 85 



ruin.* And he gives a great many examples of cases in which, in conse- 

 quence of the grubbing up of a wooded place, a torrent, which till then had 

 been inoffensive, became all at once dangerous. 



M. Culmann attaches greater importance to the initiative being taken by 

 the people, than to interventions by the Government ; and he cites facts in 

 support of his opinion. But he attaches, I may say, primary importance to 

 securing connected action by all interested ; of the advantages of which, and 

 the disadvantages arising out of the want of it, he gives facts in ilhistration. 



Proceeding to the consideration of mechanical works of engineering, he 

 recommends — (1) The clearing of the water-courses of aU large blocks resting 

 there, in which he is supported by M. Cfeanne ; (2) The erection, when and 

 where it may be expedient, of harrages and dykes or embankments. 



" In regard to such worlss, the theory of M. Culmann," says M. Cezanne, 

 " may be stated thus : — Barrages are but a temporary expedient to be 

 employed while awaiting rehoisement ; it is necessary to construct them in a 

 series, commencing from below ; when the first barrier is filled to the level 

 with gravel, then should be constructed a second behind it, and so on 

 continuously." 



Barrages are the preferable structures to erect against torrents, dykes or 

 embankments against rivers. With these, as with harrages, it is necessary 

 to proceed from below upwards. 



Barrages constructed of faciues or of wood, &c., when but a temporary 

 eifect is to be produced, are often preferable to those of stones or of masonry, 

 because they accommodate themselves to movements in the bed. Structures 

 of facines form a moveable enclosure, on which vegetation easily establishes 

 itself ; harrages, constructed with hurdles, are very useful in ravines, and 

 even on sinking slopes ; but in general stone-works are preferable to those 

 constructed of wood ; these, however, are very serviceable in cantons in 

 which the population employ them. "All the harrages in torrents con- 

 structed hitherto in Switzerland," says he, "have proved beneficial; all 

 the people who have made use of them have showed themselves satisfied 

 with them." 



Epis, or stakes, avail nothing against toiTents, or against mountain rivers ; 

 they are available only against peaceful rivers, bearing along but little solid 

 matter suspended in their waters, and this composed only of sand and 

 small gravel, and not of blocks, which are able to attack the bank and 

 change the direction of the liquid stream. " The stockade of these," M. 

 Culmann says, " should form a continuous line ; for if some do not reach to 

 this, and others go beyond it, the current, thrown from one bank to the 

 other, may do greater damage than if there had been no works of enclosure. 

 The epis, or stakes, should be sufficiently close to the bank to prevent any loop 

 or expansion of water being formed between them ; and the ' less the banks 

 the closer should they be. In mountain banks the space is so limited that 

 continuous dykes are less costly. 



" In Bavaria, for example, the lower Danube is too smaU to allow of the 

 system of stockade being applied ; they are under the necessity of adding a 

 more or less extended wing to the back of each spike — that is to say, to 

 construct immediately a portion of the future bank. They have also aban- 

 doned the system of spikes along the Ehine, where they were greatly 

 attached to it, and where they now construct continuous embankments of 

 facines. Stakes can no longer be employed along the Lech ; and since the 

 alteration of the course of the Linth, they have become satisfied that parallel 



