7(> Intelligence and Miscellaneous Articles. 



If the conducting shells are destitute of rigidity, and firmly con- 

 nected with the dielectric, upon each superficial unit of its inner 



surface the pressure - — ^ — a — - acts, and upon the same of its 

 outer surface wa 



jp 2 D 2 (l-fc)(a+ft)' 



Sira 4 * 2 



The dilatation of volume effected by these forces, referred to the 

 unit of volume, is 



Av _ 3p 2 D 2 [2\ + 2 / i-fr(A + 2 / i)] 

 v 167r/x(3\H- 2/i)a 2 



If the dielectric fills in the same manner the space between two 

 coaxial cylindrical surfaces of radii a and a + a, to the elastic force 



Jcp 2 a 2 D 2 

 Rj there is added -~ — j-^- 9 and the pressure-forces 



Stto, 2 8va*a* 



act upon the unit of the inner and of the outer surface. The elon- 

 gation thereby produced of the unit of length of the hollow cylin- 

 der is 



AZ _ p*kkD 2 



I 16irfx(Sk+2fi)a: j ' 



Therefore, for D = oo , — =3 — ; and for a lower value of D, 



A A7 V I 



— > 3 — . The former case could be approximately realized for 



glass. Both quantities are independent of r, directly proportional 

 to^> 2 , inversely to a 2 . According to this, Eontgen's view may be 

 justified, that Quincke's observations form at least no refutation of 

 the explanation of electrical expansion from the ordinary forces 

 of electric action at a distance and elasticity. An ordinary 

 Franklin's plate of the thickness a must then behave (for instance, 

 even in regard to its optical properties) as if it were compressed by 



p 2 D 2 

 the force £ — - upon the superficial unit. After this the construc- 

 tion of the general equations for the deformation of a dielectric 

 body by electrification, or of a magnetic body by magnetization, 

 presents no further difficulty. — Kaiserl. AJcad. der Wissensch. in 

 Wien, 1880, no. xxiii., JSitz. math.-naturw. Classe, Nov. 4, 1880. 



ON THE ABSORPTION OF SOLAR RADIATION BY THE CARBONIC 

 ACID OF OUR ATMOSPHERE. BY DR. ERNST LECHER. 



Experiments having already been made by Magnus and Tyiidall, 



