370 Miscellaneous Intelligence. 



.honour to M. Dufour. It was not quite finished at the time when 

 M. Pictet wrote his account of it, but would be completed in a few 

 days more. It had been planned and executed in the short space 

 of six months. Its expense was previously extimated at 16,000 

 francs, and the cost amounted to within one or two hundred francs of 

 that sum. This accuracy of estimation is not the least merit of M. 

 Dufour, the engineer. The expectations with regard to the duration 

 of the bridges are all in their favour; the iron is defended from rust 

 by a thick coat of paint, which is to be renewed when required ; the 

 Avood-work is of select materials, and not being any where in contact 

 ■with the earth is not liable to rot. 



Before constructing the large bridges, a model was made 38 feet 

 long, and having only two suspending lines each composed of 12 

 wires of .073 of an inch in diameter. The foot-way was constructed 

 on 11 wooden traverses, which hung from the suspension lines each 

 by only four single wires, two at each end. This bridge was sub- 

 mitted to the roughest trials on the part of those persons who were cu- 

 rious to examine it, such as leaping, marching, fyc, but without the 

 least accident or failure. — Bib. Univ. xxiii. 305. 



3. Hydraulic Experiments on the Propagation of Waves, by M. 

 Bidonc of Turin. — The following is the translation of an extract 

 made by M. Hachette, and inserted in the proceedings of the Philo- 

 matic Society. M. Bidone proposed to compare the results of expe- 

 riments on the propagation of waves, with those deduced from the 

 theory published by M. Poisson, in the Memoires of the Academy 

 lSlG. This theory supposed that the waves were produced by a 

 solid segment of a given figure slightly immersed in the fluid, and 

 which after having allowed time for the fluid to assume a state of re- 

 pose, is suddenly withdrawn in a vertical direction. 



M. Bidone observes, that the body rapidly withdrawn, is followed 

 by a column of water which rises above the level, and produces on 

 descending, waves which are propagated in the same time with the 

 primitive waves. Two causes concur in this elevation of the column 

 of water, the pressure of the atmosphere, and the adhesion of the 

 fluid particles to each other and to the body immersed. The height, 

 the volume, and form of the column, depend on the figure of the 

 segment immersed, and principally on the rapidity with which it is 

 withdrawn. M. Bidone mentions many examples of raised columns 

 of water, obtained by plunging successively a cone, a paraboloide of 

 revolution, a cylinder and hemispheres, but his principal object being 

 to produce undulations due to the cavity of the plunged segment, and 

 the mere action of gravity, and to approach as nearly as possible to 

 the hypothesis of M. Poisson, he has observed the primitive Avaves 

 propagated at the surface of the liquid, at the instant when the re- 

 moval of the body from the water commenced. The time which 

 intervenes before the adhering column of water begins to fall, is more 

 or less according to the height and figure of the column. When the 



