Dr. Young's Lecture, &c. 
found to be thus only reducible to a perfect analogy with other 
facts, and to the simple principles of the undulatory system . It is 
presumed, that henceforth the second and third books of New- 
ton's Optics will be considered as more fully understood than 
the first has hitherto been ; but, if it should appear to impartial 
judges, that additional evidence is wanting for the establishment 
of the theory, it will be easy to enter more minutely into the 
details of various experiments, and to show the insuperable dif- 
ficulties attending the Newtonian doctrines, which, without 
necessity, it would be tedious and invidious to enumerate. The 
merits of their author in natural philosophy, are great beyond all 
contest or comparison ; his optical discovery of the composition 
of white light, would alone have immortalised his name; and the 
very arguments which tend to overthrow his system,, give the 
strongest proofs of the admirable accuracy of his experiments. 
Sufficient and decisive as these arguments appear, it cannot 
be superfluous to seek for further confirmation; which may with 
considerable confidence be expected,’ from an experiment very in- 
geniously suggested by Professor Rokison, on the refraction of the 
light returning to us from the opposite margins of Saturn's ring ; 
for, on the corpuscular theory, the ring must be considerably 
distorted when viewed through an achromatic prism : a similar 
distortion ought also to be observed in the disc of Jupiter; but, 
if it be found that an equal deviation is produced in the whole 
light reflected from these planets, there can scarcely be any re- 
maining hope to explain the affections of light, by a comparison 
with the motions of projectiles. 
