PHYSICAL SCIENCE. 35 



transmission to circuit-currents so vast in length, and in 

 which the opposite polar forces are maintained even though 

 half the circuit be made through solid earth ? We can only 

 refer these and other questions equally obscure, to the labours 

 of a future time. 



The researches and successes of our own day are the best 

 augury for this future. Many recent discoveries, simple 

 and limited in their origin, have become volumes of new 

 knowledge in their progress. Such are, for instance, the dis- 

 covery of Oersted, on which depends the whole science of 

 Electro-magnetism ; the doctrine of Electrolysis, as finally 

 established by Faraday, in strict fulfilment of the law of 

 definite proportions ; the further discovery of Faraday, that 

 all matter of whatsoever nature, solid, fluid, or gaseous, is 

 affected in a determinate manner when placed within the 

 sphere of lines of magnetic force ; and his contemporaneous 

 discovery of the rotation of a beam of polarised light under 

 the influence of magnetic force directed through glass of a 

 certain texture ; followed by those larger researches (in which 

 Pliicker and Tyndall have partaken) disclosing relations 

 between magnetic force and the intimate structure of all 

 crystalline bodies. Many similar instances might be given, 

 but these will suffice for the purpose we have before us. 



Some single and unexpected observation may, perchance, 

 furnish hereafter a clue to the truths still desired ; and in 

 the beautiful experiments recorded in the Bakerian Lecture 

 and other later papers of Mr. Gassiot, we willingly recog- 

 nise one avenue through which such research may well be 

 directed. No one can have witnessed the wonderful pheno- 

 mena of stratified light, as seen in the luminous discharges 

 of a voltaic battery or induction-coil, passing through vacuum 

 tubes of different degrees of exhaustion, without noting in 

 these phenomena the elements of future discovery. The 

 relation of the luminous strata so produced to the electrodes 



D 2 



