174 FRESNEL. 



gance and with grace. Also I could not but persuade 

 myself that the indulgence of the Academy presaged in 

 some degree that with which the public would deign to 

 honour me ; otherwise could I have dared to make an 

 inexperienced voice heard here, after the eloquent inter- 

 preter whom we have just lost, and by the side of him 

 whom we have the happiness still to possess ? 



I hasten, moreover, to explain that this eloge departs 

 fi'om the ordinary form. I shall even ask the favour of its 

 being looked upon as simply a scientific memoir, in which, 

 taking occasion from the labours of our late associate, I 

 have the opportunity of examining the progress which 

 has been made in our times in several of the most impor- 

 tant branches of optics. At an epoch when the courses 

 of lectures at the College de France, of the Facvlte de 

 Paris, of the Jardin du Roi are attracting so great a 

 concourse of auditors, it has occurred to me that the 

 Academy of Sciences might directly address itself to the 

 public (that friend of our studies, showing its good will 

 by so numerous an attendance at our meetings) on some 

 of the various questions with which we are specially occu- 

 pied. At the same time this is but a simple attempt of 

 my own on which I should wish to be enlightened ; the 

 critic will find me docile. I hope, however, that the satis- 

 faction of becoming initiated in a few minutes into the 

 most curious discoveries of one century, may appear a 

 sufficient compensation for the inevitable tediousness 

 which so many minute details must cause. 



For my own part, the indulgence on which I count 

 will not prevent my making every effort to render myself 

 clear. Fontenelle, on a similar occasion, asked of his 

 auditory (I quote his own expression) " the same atten- 

 tion which they would necessarily give to the romance of 



