in the experiments of Fraunhqfer. 113 



interest as being the last production of that distinguished phi- 

 losopher. At any period of our history the loss of such a man 

 would have been deemed irreparable, but in the present de- 

 clining state of the arts and sciences in England, it cannot but be 

 regarded as a national calamity. In less than one year we have 

 lost two of the greatest ornaments of English science since the 

 days of Newton, — Dr Wollaston and Dr Young ; and the 

 grief which such events inspire, is embittered by the recollec- 

 tion that no national honour attended the triumphs of their 

 genius, and with the fear that none will be paid over their 

 tomb. That country must be indeed degenerate, where its re- 

 wards are conferred only on feats of animal courage, and where 

 the flower of its intellectual chivalry is allowed to live and die 

 unhonoured. 



" The following note forms a very simple corollary to the 

 Jaw of interference, by which I succeeded, some weeks ago, af- 

 ' ter having read the excellent treatise by Mr Herschel on Light, 

 in explaining the character of the perfect spectrum formed by 

 diffraction in the fine experiments of the late M. Fraunhofer. 



" It has been long ago observed, and Dr Brewster, if I am 

 not mistaken, made the remark, in treating of the superficial 

 colours of mother-of-pearl, that the images seen in this case of 

 multiplied diffraction approached nearer the solar spectrum 

 formed by refraction than the prevalent colour of ordinary dif- 

 fraction, or those of the rings analyzed by Newton. But it is 

 to M. Fraunhofer that we owe the most precise experiments 

 on these colours. 



" The following is the principle by which I propose to ex- 

 plain this phenomenon. If there is a series of parallel lines 

 capable of furnishing by pairs the ordinary colours of diffrac- 

 tion, the union of a considerable number of these lines ought 

 to have the effect of narrowing extremely the fringes formed 

 by homogeneous light, so that after the brilliant central line 

 there ought to be some total darkness ; that is to say, in place 

 of the second brilliant band of the narrowest fringes, which the 

 two parallel lines the most remote would have formed ; and 

 this darkness will be followed only by paler bands of light, 

 which will go on diminishing to half the distance of the second 

 principal brilliant line of any single pair of adjacent lines. 



NEW SERIES. VOL. I. NO. I. JULY 1829. H 



