462 Royal Society : Prof. Faraday's Fourteenth Series 



Viewed by one eye alone the outline may with equal ease be ima- 

 gined to be either ; but when the two monocular pictures are viewed 

 one by each eye, the proper or the complemental form may be fixed 

 in the mind ; the former, if the right and left pictures be presented 

 respectively to the right and left eyes ; and the latter, if the right pic- 

 ture be presented to the left eye, and the left picture to the right 

 eye. Many new experiments are then detailed, and a variety of in- 

 stances of false perception of visual objects, some new, others former- 

 ly observed, are traced to these principles ; among others, the well- 

 known apparent conversion of cameos into intaglios. The author 

 next proceeds to show that pictures similar in form but differing in 

 magnitude within certain limits, when presented one to each eye, 

 are perceived by the mind to be single and of intermediate size ; and 

 also that when totally dissimilar pictures, which cannot be combined 

 by the mind into the resemblance of any accustomed objects, are 

 presented one to each eye, they are in general not seen together, but 

 alternately. The memoir concludes with a review of the various hypo- 

 theses which have been advanced to account for our seeing objects 

 single with two eyes ; and the author states his views respecting the 

 influence which these newly developed facts are calculated to have 

 on the decision of this much-debated question. 



" Experimental Researches in Electricity," Fourteenth Series. 



On the general nature and relation of the Electric and Magnetic 

 Forces. By Michael Faraday, Esq., D.C.L., F.R.S., &c. &c. 



The author commences by observing that the theory of electrical 

 induction, which he had set forth in the 11th, 12th, and 13th se- 

 ries of researches*, does not assume or decide anything as to the 

 real nature of the electric forces, but only as to their distribution ; 

 the great question respecting the existence of any electric fluid, or 

 of one, or of two fluids remaining untouched. He then states what 

 the theory does assume ; as, for instance, that all particles, whether 

 of insulators or conductors, are, as wholes, conductors ; that, being 

 conductors, they can readily be charged either bodily or polarly ; 

 that contiguous particles being on the line of inductive action can 

 communicate their forces more or less readily; that those doing so 

 most readily constitute the bodies called conductors, and those do- 

 ing so least readily those called insulators, &c. 



Having thus given a brief summary of the conclusions drawn 

 from the previous investigations, the author proceeds to consider 

 the particular condition of the particles which, in an insulating 

 body, are considered as polarized ; and after showing that the 

 theory requires that they should be able to polarize in any di- 

 rection, he states his expectation that a greater facility to polarize 

 in one direction than another would still be found to belong to 

 them, and proceeds experimentally to determine this point. His ex- 

 periments were made by observing the degree of inductive force 

 across cubes of j^erfectly crystallized bodies, as rock crystal and 



* Prof. Faraday's Eleventh Series of Researches will be found at large, 

 in the present voUime, at p. S81 et seq.; and abstracts of the Twelfth and 

 Thirteenth Series, in vol. xii,, p. 42Q and 430. 



