of the Water ofNutsMll Spring. 419 



bitter, and its specific gravity 1-0121. From the imperial 

 gallon of this water I obtained 



Chloride of iron . . 34*126 grains 



Chloride of calcium . 308-777 



Common salt . . . 620-614 



Silica 1-333 



964-850 

 In an imperial quart, which was all of this water that I 

 had to analyze, I could detect no sulphate even when the 

 liquid was concentrated to a tenth-part of its volume. The 

 imperial gallon contained two cubic inches of sulphuretted 

 hydrogen gas. The common salt extracted from Nutshill 

 water contained a notable proportion of iodine — indeed a 

 much greater quantity than I have met with in any other 

 mineral water, that I have subjected to analysis. 



ARTICLE V. 



On the Connexion between Refracted and Diffracted Light. 

 By Paul Cooper, Esq. 



(Read before the Royal Society, 8th May, 1834.) 

 ( Concluded from page 355. ) 

 The difference in the breadth of the fringes, when the 

 screen is placed at different distances from the object, as in 

 the third observation, proceeds from the developement of 

 the different colours by divergement, upon the same prin- 

 ciple that the spectrum is formed upon a screen, when the 

 light is refracted by a prism. The rays of different colours 

 which cross each other, and form white light at the edge 

 of the object, open at this ipoint at the same angle as that 

 by which they approached it, and, of course, the farther 

 the screen is removed from the object, the more the colours 

 are separated from each other, and, consequently, the 

 broader the fringes. 



The curved form of the line joining the same point of 

 the fringe at different distances behind B, arises from the 

 intersection of rays, the refraction of which, from having 

 passed through different parts of the lens, is constantly 

 changing with the distance; it is, therefore, correctly 



