Intelligence and Miscellaneous Articles, 491 



from layer to layer moves is then equal to the velocity of a molecule 

 estimated in the direction of the diagonal. The length of this 

 diagonal is \^3, when 1 equals the length of a side of the cube. 

 The cosine of the angle which is formed by the diagonal and the 



side of the cube equals therefore — 7=.. Let u be the velocity of 



a molecule, then the component of the same, estimated from the 

 normals, is 



Let p be the pressure of the gas against the unit of surface, v a 

 certain volume, n the number of molecules in the same, and m the 

 magnitude of a molecule, then, according to the theory developed by 

 Kronig and Clausius, we have the relation 



nmu 2 

 pv= . 



Putting — =p 



where p means the specific gravity of the gas, we have 



and accordingly w= \/ * 



which is Newton's formula for the velocity of the propagation of 

 sound. 



A more complete theory of the propagation of sound, grounded 

 upon the new notions about the construction of gases, requires 

 moreover that Laplace's correction should be applied to the above 

 formula. In order to arrive at this, it is necessary to enter into the 

 irregularities in the movements of the molecules, and perhaps also 

 to consider the circumstance that, as Clausius has shown, over and 

 above the progressive motions of the molecules, motious must take 

 place in the molecules themselves. 



The above disposition of the elementary cubes is also applicable 

 to the theory of the conduction of heat, when the object in view is 

 only to obtain an approximative value of the conducting-power. — 

 Poggendorff's Annalen, No. 3, 1863. 



Vienna, 13 March, 1863. 



ON THE ORIGIN OF AMYGDALOID ROCKS. 

 BY DR. TSCHERMAK*. 



The general opinion in regard to these rocks is that they are of 

 igneous origin, — in fact, that they are a sort of lava whose vesicular 



* Communicated by Count Marschall. 



