290 ANNUAL, EEPORT SMITHSONIAN INSTITUTION, 1910. 



of internal movement, the relation between these movements and the 

 properties of the magnet, and the possibility of transmutation. 

 These ideas Ave are always calling to our aid in practical work. I 

 may quote here a few lines of Lucretius which are truly prophetic : 



" Versibus ostendi corpuscnla material 



Ex iufluito suimnam rerum usque teuere 



Undique protelo plagaruin continuato." 



(The corpuscles, the elements, of matter shall preserve for all eternity and 

 everywhere the uniformity of things by a scries of ever-continued blows.) 



" Fit quoque ut hue veniant in coeluni extrinsecus ilia 



Corpora quae facient nubes nimbosques volantes." 



(It may happen that hither from the worlds beyond may come those bodies 

 which form the mists and the flying clouds.) 



According to Lucretius these corpuscles are innumerable and 

 traverse rapidly inexpressible distances, so that you may recognize in 

 these citations the principal properties which we attribute to-day to 

 electrified corpuscles. 



However, if certain of these ideas which have just been expounded 

 have inspired philosophers and savants of all ages from antiquity 

 to the present day, still, the idea that electricity can give birth to 

 matter is entirely modern and is due to the discoveries of radio- 

 activity (February, 189G) , of the Zeeman phenomenon (August, 1896) , 

 and of the nature of cathode rays (1895-1897). 



Between the assertions of the ancient philosophers and those of our 

 day there exists a profound difference. The former were never sub- 

 jected to any experimental confirmation; they were merely concep- 

 tions of the imagination and their value is limited by the errors which 

 they included. The latter, however, can be justified by experiments 

 which brook no contradiction and by reason of this confirmation 

 carry conviction with them. 



