420 The Rev. S. Hanghton on the ThicJcness 



It is ft fact, however, that when iny collecting sphere is con- 

 nected by means of an insulated wire with the electrometer, the 

 latter always indicates the presence of electricity opposite in kind 

 to that which the sphere brings down when charged in the ordi- 

 nary manner. It follows from this, as Peltier, sen. has always 

 asserted, that the sphere is actually charged by induction and 

 not by conduction, so that the air is electric. How could 

 the increase of aerial electricity with the height be explained if 

 this electricity proceeded from the earth ? For in the latter case 

 it must diminish v.^th the height. j\Iist is known to increase 

 the atmospheric electricity; and yet, coming from below, it should 

 bring with it electricity from the earth, and thus weaken that of 

 the air. The greater atmospheric electricity of whiter appears 

 to me to arise merely from the greater frequency of mists, just 

 as the daily variations of this electricity may be quite well ac- 

 counted for by the quantity of mist. 



The views of Peltier, jun. and Lamont appear to lead only to 

 complications and contradictions. On the other hand, in order 

 to progress in this field, it will be well to pursue further the 

 researches on ozone commenced by Schonbein, and the views on 

 the diamagnetism of oxygen to which Faraday has been con- 

 ducted. 



Of course a multiplicity of observations and many new expe- 

 riments will be necessary before the phajuomena can be brought 

 under general laws, and their causes satisfactorily stated. It 

 is precisely on this account that it becomes advisable not only to 

 increase the number of stations where such observations can bo 

 made, but also to agree upon some system of cooperation. 



Kreutznach. January 1853. 



LXIII. On the Thickness of the Earth's Crust. By the Eev. 

 Samuel IIaughton, F.H.S., Pi-ofcssor of Geology in Trinity 

 College, Dublin. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



IN your Number for the present month (October), Archdeacon 

 Piatt replies to the short statement I made in the June 

 Number respecting my paper " On the Original and Actual 

 Fluidity of the Earth and Planets*." 



The questions at issue between us are two in number, viz. — 

 1. AA'hether I have committed a fallacy in mathematical rea- 

 soning, by differentiating a certain equation in my paper pub- 



* Transactions of the Royal Irish Academy, vol. .xxii. p. 251. 



