DISCOVEKIES OE SIB ISAAC NEWTON. 459 



doing this. Seldom, indeed, is it that we find in any one individual 

 more than one of these distinct functions eminently developed, yet 

 Newton takes foremost rank in all. There have been experimenters 

 who have equalled, perhaps surpassed him in fertility of device and 

 acuteness of observation, but in both the other classes he stauds un- 

 rivalled ; and taken in conjunction, not only is there no one like him, 

 but hardly second to him, perhaps Laplace the nearest, but that only 

 longo post intervaUo. To write then a full account of the discoveries 

 of such a man would require for the task one who is able to appre- 

 ciate him in all these departments. Now, Sir David Brewster is 

 undeniably a splendid experimental Philosopher, but we are not aware 

 that he has ever laid claim to eminence in pure, (and, by consequence, 

 in applied) mathematics; accordingly, while a great portion of his 

 bulky volumes is devoted to matter we cannot help considering irre- 

 levant, such as the lives of Tycho Brake, G-alileo, and Kepler, Lord 

 E-osse's Telescope, the discovery of Neptune, and a good deal of am- 

 bitious writing, which we could well have spared, there are but about 

 ten pages devoted to an analysis of the Principia, and those disfigured 

 by blunders, (slips we would willingly call them) which vre can hardly 

 credit our eyes on reading. Still worse do Newton's inventions and 

 researches in pure mathematics fare, numbers of them being passed 

 over without comment, some not even mentioned. To make up for 

 this omission we have nearly a third of the work taken up by the 

 optical researches of Newton and of others, both before and after 

 him. Now, Newton's discoveries in optics, though enough to make 

 half-a-dozen reputations, are those on which his fame least rests, for, 

 though he discovered the composition of colours in white light, by an 

 accident of manipulation he missed its corollary, the irrationality of 

 dispersion ; and though his experiments on the colours of plates and in 

 diffraction and interferences, were beautiful and valuable, yet by an 

 accidental mismeasurement he was confirmed in referring them to a 

 theory which is now universally rejected. The relation between 

 Newton and his Biographer is here somewhat curious. Newton's 

 analysis of the solar spectrum was met at first by much opposition and 

 controversy, though it speedily triumphed over assault, and has been 

 accepted by all down to the present time, (except, indeed, by Goethe, 

 of whom we need not here speak) when it has found an assailant in 

 Sir David himself. The substitute proposed by him he has been 

 unable to persuade his contemporaries to accept, and thus in the 

 present work wo find a running parallel implied between Newton and 

 his detractors on the oik; hand, and Sir David and the present gene- 

 ration on the other. Newton condescended to reply with great tern- 



