Si Experiments and Obfervations oti'^Light. 



that by the approach of the edges the diftances of the fringes therefrom are not increafed or 

 cka/iged, but that the bendings of the rays are thereby increafed, and that the neareft knife 

 determines which way the ray (hall be bent, and the other iiicreafes the bent. Obfervation 

 I, repeats the experiment, and (hows how by the inclination of the edges all the ap- 

 pearances which at diiPerent times were before produced by the fucceflive approach of the 

 edges, are now all at_ one time exhibited at their dilFerent diftances from each other. 

 The fringes where the edges are diftant are formed in the light rendered divergent by the 

 fmall hole, where they appear to have croflcd they are made by each remote edge in the 

 light bent by the neareft edge, in light which, if the remote edge was abfent, would there 

 form the fringes of the neareft edge; upon the approach, therefore, of the knives, the 

 diftances of the fringes of each knife are changed and increafed, contrary to what Newton 

 obferves, for they are then made in light beyond that of the (irft fringes of each edge, that 

 light neareft to each edge compofing then the fringes of the remoter edge, and as each edge 

 thus makes its fringes in the light bent by the oppofite edge, the nearer it approaches in 

 more bent light will the fringes be made ; not that the approach bends the light, it lelTens 

 the bent by contrary attraftion, but changing at the fame time the light of the fringes, it 

 makes them in other light nearer to the bending edge, and, therefore, more bent than the 

 former light, and, therefore, the fringes are alfo broader. This making of broader fringes 

 in light more bent led Newton into a wrong conclufion. The light does not increafe its 

 bending and divergence, the fringes change their light: by the approach of the edges 

 they are made in light more bent and diverging, but the general bent of the rays is really 

 diminipjed by that approach, and whilft the neareft knife continues to bend the rays to- 

 wards itfelf, the otlier knife dim'wi/bes that bent. 



In obfervation the ninth, Newton having meafured at different diftances from the 

 knives the dimenfions of the fringes, , intervals, and (hadows, and finding that the dif- 

 tances of the point of crofTing of the dark lines between the firft and fecond fringes from 

 that of the concourfe of the (hadows of the edges, continually increafed, and taking it for 

 granted, contrary to the fa£l, that thefe gave the true meafures of the diftances of pafTage 

 of the light itfelf from the concourfe of the edges, concluded, that the light which made 

 the fringes was not the fame light at all thofe diftances, but pafTed nearer to the knives, and 

 was more bent when the fringes were obferved at fmall than at greater inftances. Obferva- 

 tion M, (hows that thefe increafed dimenfions are merely produced by the divergency of the 

 light of the experiment, a circumftance which efcaped Newton in his firft obfervation 

 alfo, and that, confequently, the fringes are always the fame at all diftances of obfervation, 

 and are made in the fame light equally bent, and paflTing at the fame diftance from the 

 edge. 



Obfervation the tenth of Newton is employed in an attempt by aftual meafurement 

 to afcertain the nature of the curves formed by the fringes and intervals in the preceding 

 experiment. They are determined to be hyperbolic, and their afymptotes drawn. The 

 fringes themfelves are by him feparated, and diftinguifhed from another triangular light, 



3 fuppofed 



