164 Miscellaneous Intelligence, 



lately made a beautiful application of M. Chladni's mode of exhibit- 

 ing the nodal lines of vibrating elastic laminae, in the examination of 

 the structure and elasticity of various solid bodies, such as crystals, 

 wood, stone, &c. &c. ; or rather, resorting to M. Chladni's mode of 

 rendering these lines visible by small particles placed on the surface 

 of the plates, he has, by means of these lines, instituted an inves- 

 tigation of various physical properties of solid bodies ; and since he 

 has made this application, it has been found that the phenomena in 

 question afforded a method of examining the internal structure of 

 bodies, in some cases far surpassing in sensibility the power of 

 polarized light, and applicable, in innumerable instances, where the 

 latter would be of no avail. 



Lately, he has applied the same means of investigation to the 

 metal bodies, which up to this time have been considered, amongst 

 solid substances, as those approaching the nearest to homogeneity. 

 They have been regarded as assemblages of infinitely small crystals 

 united without order, and no one suspected that, in an ordinary 

 mass of metal, there might be differences of cohesion and elasticity 

 as great or greater than those observed in fibrous bodies, such as 

 wood. Nevertheless, experiment shews that circular plates of 

 metal of uniform thickness, whether cast in moulds, or cut out of a 

 solid block, or taken from rolled plates, act under the influence of 

 sonorous vibrations as if they belonged to fibrous bodies, or those 

 regularly crystallized. When a solid substance, perfectly homoge- 

 neous and uniform in its structure, is formed into a circular plate of 

 even thickness in every part, if this plate be sustained horizontally 

 by small surfaces of support, applied above and below at the centre 

 only, and sand be sprinkled on the plate, and a violin bow applied 

 carefully at the edge so as to produce the lowest possible sound, 

 the nodal lines will be indicated by the sand arranging itself into 

 two true diametrical lines, crossing each other at right angles ; and, 

 by varying the place to which the bow is applied, these diameters 

 may be made to occur in any part of the plate. But if the sub- 

 stance be not similar in structure in every direction, then this mode 

 of division cannot be effected in every direction, and the nodal 

 lines become hyperbolas, which are frequently accompanied by 

 sounds varying from each other, sometimes almost insensibly, at 

 others differing by as much as a third, a fourth, or even a fifth. 

 Hence is derived a means of distinguishing between substances 

 which are of perfectly uniform structure, and those which vary in 

 different directions, as crystallized and fibrous bodies. - 



Plates of gold, silver, copper, zinc ; cast, forged, and rolled iron; 

 tin, lead, bismuth, steel, antimony, and a great number of alloys, 

 as brass, bell-metal, &c, have presented properties analogous to 

 those of rock crystal or wood, when cut into plates oblique to the 

 axis of elasticity or to the cleavage. 



The fact being ascertained, that a plate of metal may always be 

 considered as if in its structure it belonged to a crystallized system, 



