So New Publications. 



light, but by a faint light irregularly fcattered in every di- 

 rection from that beam : and a light fo faint would fcarcely 

 be equal to the production of the many-coloured irides round 

 the fun, moon, &cc. in the circumftanccs in which thefe ap- 

 pear; nor, indeed, could the globules of water fall under any 

 light fo faint, where the main beam to whieh they are ex- 

 pofed is broader than their whole furfaces. 



On the other hand, the author of this effay has obferved 

 that the arrangement of the colours and orders of colours in 

 the manv-coloured irides of which he treats, is not only im- 

 poffible by any refraction that can be fuppofed ; but is per- 

 fectly the fame with the arrangement of the colours in the two 

 fets of fringes into which a ray of while light, admitted into 

 /i dark chamber, and made to pafs between two parallel edges^ 

 is naturally divided. Each of thefe two fets of fringes, if 

 taken outward from the central line, exhihils precifely the 

 £ime arrangement of colours, as does the folar iris taken 

 from its interior to its exterior extremity. He therefore 

 concludes that, in the formation of the many-coloured irides, 

 the fun's irradiation, pafing between the edges of contiguous 

 drops of water in the aimnlpbcre, is, by the infecling attrac- 

 tion which thefe exercjfe upon it, feparated into two fets of 

 fringes, which fringes conjiiliite lie i.idcs, having the body 

 of the fun for their central line. This is the author's theory. 



It is at lead admirably ingenious; more fimple and plau- 

 fible than that which it ftrives to furperfede; and founded 

 upon a better induction of unquestionable facts. We fhould 

 hope that the general difcufhon of philofophers muft finally 

 eftabllfh it as fcientiiie truth. The cflay is elegantly and 

 unaffectedly written. 



A Treat) fc on the Chemical Hijlory and Medical Powers of 

 fame of the mrf celebrated, Mineral Waters, &c. P>y 

 William Saunders, M.D. F.R.S., &c. Phillips, 

 George-yard, Lombard-ftreet. 8vo. ' 483 Pages. 



THE more accurate analyfis of mineral waters by mo- 

 dern chemiftry, cannot but lead national phvficians to efti- 

 mate more juftly than before, the nature of their refpective 

 medicinal powers. 



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