T0BRENT8 OF THE HIGH ALPS. 45 



has called for special legislation ; and to this legislation on the subject a 

 chapter is devoted. The legislation referred to is embodied in the DScret 

 du 4 Thermidor an XIII. relatif aux torrents du department des Sautes 

 Alpes. It is given in fuU in an appendix to the work, with much additional 

 information in regard to the subject ; and in the text is given a succinct 

 account of the working of the law, with Ulustrations in justification of the 

 same. From this it appears that when a new bank of a certain extent is 

 ravaged by a torrent, the proprietors meet together and constitute a 

 syndicat, or court, a requisition is addressed to the prefect, he commissions 

 a civil engineer, ofiScially connected with the department, intrusted with 

 the construction and conservation of roads and bridges — ingenieur des ponts\ 

 et chaussees, — to examine the ground, and, if it be necessary, to report the 

 works proper for the defence of the bank. r 



The work is executed in accordance with the adjudication ; the engineer 

 superintends the construction, and sanctions the delivery of it ; and the 

 expense is borne by those interested, shared according to a scheme of 

 division prepared by the syndic. 



A translation of the decreet wiU be given in the sequel. 



Attention is next given to the different modes of constructing the 

 defences — (1) Levee en Perri ; (2) Walls built with lime; (3) Drystone 

 walls ; (4) Ghevalets ; (5) Coffres. 



The first is employed by preference in longitudinal embankments ; the 

 three last mentioned are rarely employed but in the construction of 6pis ; 

 lime-built walls are employed in both forms of defence ; the chevalet is a 

 wooden erection of three pieces of timber stuck into the ground, apart 

 below, meeting above, and sustained by a fourth piece stuck into the 

 ground behind them, meeting them at the apex of the angle formed by 

 them ; cofires are quadrangular structures of timber, the interior of which 

 is filled with stones ; the levie en p&rr% is an embankment of earth faced 

 with stone. 



A chapter is devoted to the consideration of a form of embankment called 

 Bique ^peronnS or spurred embankments. 



Another is devoted to the consideration of the encaissement or confining 

 of torrents, the outline to be given in the encaissement in section, the direc- 

 tion to be given to the axis of the course, and the declination to be given 

 to it. This is followed by a chapter devoted to the consideration of 

 different systems of defence which have been proposed ; and three ehapters 

 which follow are occupied with the condition of roads swept by these 

 torrents, details of what measures are requisite to remedy existing evils, 

 and of measures to be adopted in erecting bridges over the torrents. These 

 constitute the third part or division of the work. 



The ground being thus cleared, M. Surell proceeds, with a view to the 

 adoption of less objectionable and more appropriate remedial applications, 

 to bring under consideration the causes of the formation and of the violence 

 of the torrents, and with this the fourth part of the work is occupied. 



In discussing the foreign influences which have modified the primitive 

 condition of the Alps, and produced definite efiects on the formation or 

 extinction of torrents, lie gives prominence to the influence of forests. In 

 successive chapters he discusses the influence of forests on the formation of 

 torrents, and the influence of forests on the extinction of torrents, the decay 



