VISCIDITY OF WATEtt. 157 



nea may differ in different subjects, and have not, that wantlngfordis- 



' n visiou ^ 

 water. 



I know of, been well determined, I shall not attempt to ^^^ 



treat this inquiry on the strict principles of optics ; but 



only observe that I was then able to do by adjustment of 



the organ^ what would now require the assistance of a 



four inch lens ; and that I do not apprehend that I could 



thep, or that any one else can, see distinctly in the air at 



two inches distance. But this appears necessary to be 



done by an eye like mine in order to see underwater. 



A certain part of the refraction performed by the eye 



is effected by the anterior surface of the cornea, and the cornea the less 



rest by the internal structure. Two eyes may be so would an eye 



be affected by 

 constructed, as that in one of them the cornea may per- immersjon in 



form a very considerable part, and in the other, the greater water, 

 part may be effected by the internal structure ; and both 

 these eyes may see equally well : but they would not 

 both be alike affected by immersion in water. That with 

 the most prominent cornea would afford the least distinct- 

 ness ; the other might be so little affected as to give dis- 

 tinct vision under water, by a change within the reach of 

 its ordinary adjustment. Do the curvatures of the cornea ^j.^ human 

 in different subjects, who see well, vary sufficiently to tyessovarious? 

 admit of this solution of our difficulty ? — This must be re- 

 ferred to experiment. 



My correspondent has offered to exhibit his experiments ^rr 

 before Hie. I shall be happy to accept his kindness, and the experi- 

 at the same time should be glad if his African friend "^cnts. 

 would look into my large jar. 



xiy. 



Experiments and Obftervations on the Adhesion of the 

 Particles of Water to each other. By Benjamin, 

 Count of Rumford^ F. R. S. Sfc . Communicated bi/ 

 tJie Author to the National Instilution of France^ and 

 transmitted to him by the Editor. 



(Continued from page 56.) 



I 



F the particles of water adhere strongly to each other. The film is 



it appears to me to be a necessary consequence that a j^e conse- ** 



ks lid of pellicle will be formed at the surface of the li- qucnce of the 



quid, and even at all these surfaces, whatever may be in adhesion of the 



^ . •' aqueous parti- 



otherdes. 



