J76 THEORY OF LIGHT AND COLOURS. 



fyftem. It is prefumed, that henceforth the fecond and third 

 books of Newton's Optics will be confidered as more fully 

 underflood than the firft has hitherto been ; but, if it mould 

 appear to impartial judges, that additional evidence is want, 

 ing for the eftablifliment of the theory, it will be eafy to enter 

 more minutely into the details of various experiments, and to 

 fhow the infuperable difficulties attending the Newtonian doc* 

 trines, which, without neceffity, it would be tedious and in- 

 vidious to enumerate. The merits of their author in natural 

 philofophy, are great beyond all conteft or comparison ; his 

 optical difcovery of the compolition of white light, would 

 • alone have immortalifed his name ; and the very arguments 



which tend to overthrow his fyftera, give the flrongeft proofs 

 of the admirable accuracy of his experiments. 

 Experiment In Sufficient and decifive as thefe arguments appear, it cannot 

 which the cor- De fuperfluous to feek for further confirmation: which may 



pulcular theory . , - \ ' V , r ~,ir • 



ought to exhibit with connderable confidence be expected, from an experiment 

 diftortion. verv ingenioufly fuggefled by Profeflbr Robifon, on the re- 



fraction of the light returning to us from the oppofite margins' 

 of Saturn's ring ; for, on the corpufcular theory, the ring 

 mull: be confiderably diftorted when viewed through an achro- 

 matic prifm : a fimilar diftortion ought alfo to be obferved in 

 the difc of Jupiter ; but, if it be found that an equal deviation 

 is produced in the whole light reflected from thefe planets, 

 there can fcarcely be any remaining hope to explain the affec- 

 tions of light, by acomparifon with the motions of projectiles. 



IV. 



An Analyfis of a Mineral Subftance from North America, con* 

 taining a Metal hitherto unknown. 5j/CharlesHatch ett, 



( Conclu dedfrom Page 1 3 3 . ; 

 H. 



The white pre- A HE white precipitate, when diftilled with four parts of 

 c £'^V? s, !^ le fulphur, remained pulverulent, and, from white, was only 



affected by dif- , „ 



tiilation of the changed to a pale a(h colour. 



fulphuric and Nitric acid was digefted on the powder, and, being heated, 



afforded fome nitrous gas; after this, the powder became 

 white., and in every refpect recovered its original properties. 



Before 



