Mr. J. Napier on the Solubility of Metals, fyc. 365 



the faces 5, 6 of the pyramid, and destroying the symmetry 

 of the picture. When all the faces but No. 6 are seen by the 

 left eye, vision is still unsatisfactory with both eyes, and yet 

 more so when only three of the faces are seen by the left eye. 



Hence we conclude that, in these cases, binocular is inferior 

 to monocular vision. 



Let us next suppose that the object viewed is a table knife, 

 so placed that, when the back of it is towards the observer, 

 the left side of the blade is seen by the left eye, and the right 

 side of the blade by the right eye. As the back is seen by 

 both eyes, the picture presented to the mind is a compound 

 of one double and two single sensations, and, consequently, a 

 very unsatisfactory representation of the object. 



Hence we conclude that, in this case, binocular is still more 

 inferior to monocular vision. 



These results stand in direct opposition to those given by 

 Professor Wheatstone, who considers it an established fact, 

 " that the most vivid belief of the solidity of an object of three 

 dimensions arises from two different perspective projections of it 

 being simultaneously presented to the mind." Before entering, 

 however, upon this branch of the subject, I must examine 

 Mr. Wheatstone's views respecting the binocular vision of 

 figures of different magnitudes. 



[To be continued.] 



LIV. On the Solubility of the Metals in Persulphate and Per- 

 chloride of Iron. By Mr. James Napier*. 



THE following observations have been lying in nn unfi- 

 nished state for some months past, in hopes that time 

 would allow me to make more investigations into some of the 

 phaenomena developed ; but owing to urgent duties, altogether 

 apart from such investigations, I have little hopes of being 

 able to fulfil these intentions ; I have therefore collected them 

 together, in hopes that it might attract the attention of some 

 one more qualified to give them that investigation which their 

 singularity seems to deserve. 



I may be allowed, in the first place, to relate the circum- 

 stances which led me to the observations which follow. Hear- 

 ing of the great quantity of water which is constantly issuing 

 from the Pary's Mines, Anglesea, impregnated with copper, 

 and the great expense of obtaining this copper, I thought it 

 probable that it might be extracted by means of a galvanic 

 current, or what is known as the electrotype process. For 



* Communicated by the Chemical Society ; having been read November 

 7, 1843. 



