253 SECTION MECHANICS. 



ON THE FLUIDITY AND FLOW OF SOLID BODIES. 



M. TRESCA : Gentlemen, when ten years ago, after many careful 

 experiments, I made use of, and commented on the scientific expression, 

 Flow of Solid Bodies, my first communications were not received 

 without some shadow of incredulity. I, therefore, feel it my duty to 

 mention with gratitude the names of Mr. Tyndall, Mr. Fairbairn, and 

 Mr. Scott Russell among the scientific men, who at the very outset, 

 interested themselves in this subject. I should wish to thank them 

 in your language, but I am afraid that I am not sufficiently familiar with 

 it, and I therefore rely on your indulgence for allowing me to address 

 you in French. 



The question of the flow of solid bodies has been a great success ; 

 it is, thanks to it that I now hold a position to which I should never 

 have dared to aspire, and which allows me to represent French science 

 at this Exhibition. We have been most desirous, I can assure you, to 

 afford you heartily all the help that lay within our power. 



The principal fact connected with the flow of solid bodies was very 

 simple. If a resisting mass, enclosed in a wrapper, be submitted to 

 an exteiior action of sufficient power, it will exert in every direction a 

 greater or less pressure, and if a hole be made in the wrapper, the 

 matter will escape through this aperture, forming a jet, which is 

 made up of different portions of the mass. When the latter is 

 homogeneous, and the shape of the mass is regular, and the hole is 

 in a certain symmetrical position with regard to it, the mode of final 

 distribution may be deduced from the mode of initial distribution, and 

 the first experiments made will determine the kinematical conditions of 

 such a flow. 



Thus, in the formation of a cylindrical block by the superposition of 

 a certain number of slabs of lead, it was found that each one of the 

 slabs penetrated by turn into the jet, and formed there a concentric 

 tube when the aperture itself was concentric. 



Why were we so astonished to find, on cutting, according to a 

 meridian plane the so formed jet, that it was composed of as many 

 continuous tubes as there were slabs, until the complete exhaustion of 

 the matter which supplied food for its formation ? Could, indeed, 



