outline briefly to you, illustrious members of the Academy, the various manners which 

 I have devised for putting a lever into motion. 



1. The first lever I have set in motion consists of a magnetized steel bar, set 

 vertically between the ends of a temporary magnet. The bar oscillates in response to 

 succeeding magnetic attractions and repulsions which take place between the S pole 

 of the bar and the S and N poles of the temporary magnet, which poles are continually 

 reversed by the same lever. By means of the same contrivance the lever can be made 

 to oscillate in a hori^^ontal plane. 



2 " 



The rest of part 4 deals in a general way with other methods of produc- 

 ing motion by the use of electro-magnets and is not of interest in this 

 discussion. 



A bi-monthly publication entitled Annali delle Scienze del Regno 

 Lombardo — Veneto, Padova, in its issue of July-August 1831, gives a 

 review of the presentation of the dal Negro paper before the Academy 

 of Padua. This review, which is more than a thousand words long, 

 covers very completely the subject matter of the first three parts of 

 dal Negro's paper. It makes no mention whatever of the new electro- 

 magnetic motor. Since the description of the motor appears to be the 

 most novel and interesting part of the paper as finally published, the 

 omission of any mention of it in the published review naturally raises 

 a question whether the description of the motor w^as a part of the paper 

 as originally presented. 



Furthermore, in the November-December 1831 issue of Annali delle 

 Scienze the first three parts of dal Negro's paper are published, but not 

 the fourth part. In this there is no reference to the electro-magnetic 

 motor except the following statement in the introductory part, given 

 as one of the reasons for presenting the paper : 



"4. Finally, because I hope to have enriched physics with a new motor, having 

 succeeded in putting into motion in various manners a lever, taking advantage of the 

 strength of temporary magnets." 



The article is marked "to be continued, " which suggests that it was the 

 intention to add in a later issue a description of the electro-magnetic 

 motor mentioned in the introduction. However, a review of subse- 

 quent issues fails to reveal any publication of part 4. 



The above evidence indicates that the brief description of dal Negro's 

 motor mentioned above probably was not published before the end of 

 1831, and raises considerable doubt whether it was included in the 

 original draft of dal Negro's paper presented before the Academy in 

 June and July, particularly in view of the lack of any mention of this 

 part of the paper in the very full report of the meeting published in 

 August. 



The first full description of dal Negro's machine was published in the 

 Annali delle Scienze for March and April 1834. This paper includes 

 the following footnote : 



10 



