154 VISION UNDER WATEn. 



perimcnts is almost as objectionable as the washing tub, 

 or wash-hand bason. I would ask if the very form of 

 your glass vessel might not have the effects of refracting 

 the rays of light, or of their crossing so as to caiiso an 

 imperfect vision of the object looked at? You of course 

 know that in our Courts of Judicature, the evidence of a 

 person swearing to a transaction seen through blown 

 glass is not held admissible ; and here I do not see, what 

 occasion there is, in making the experiment, that the rays 

 of light should pass through any other medium but the 

 water itself. Now with respect to the distance, the 

 focus was obtained under water, it appears to me not to 

 be the question, but whether the object was visible or not. 

 It so happens I am short sighted, but it surely cannot be 

 contended that I cannot see, because I hold a newspaper 

 nearer my eye than another, as the eyes of different peo- 

 ple of the same age are of different focus, but they still 

 see, perhaps equally well at their respective foci. Age 

 also will cause a difference. I have no doubt that convex 

 lenses would enable the eye to sec clearer at a greater dis- 

 tance in water, for we know the crystalline humour in 

 fish is almost globular, and doubtless for that purpose. 



In your ''conclusion that the human eye cannot dis- 

 tinguish objects under water," I think you begin to dis- 

 cover that your former opinion maij be fallacious, as you 

 are disposed to question whether some people may not see 

 itnperfecilij under water, and conclude thus ; " but I must 

 confess that I do not incline to that opinion." 

 New experi- Xhe experiments I made are these : I went en the 

 Thames" A^ Thames in a boat a little above Richmond, accompanied 

 diver brought by two friends ; we took Avith us a native of Africa who 

 up variousob- ^ jj^ j^g^jjg experiment before US : we took in the 

 jects from a , i ' /- 



depth of near boat two eggs, thinking them the most proper for trial, 



nloefeet. j-^qj^^ what youiiad stated in the 4th paragraph of your 



reply ; one of which 1 had spotted with red sealing wax. 

 I tirst threw the spotted egg into water, between eight and 

 nine feet deep, where the water was not very clear; for 

 we could fiot see the egg at the bottom from the boat: 

 our diver on the first attempt readily brought us up the 

 egg. I then threw in both, desiring him to bring up the 

 plain one only, which as readily he did, though he saw 



the 



