NOTES TO BOOK XI. 45 



should be permanently fixed, and sufficiently large, and yet 

 should in no way interfere with the motion of the rigging, 

 or with the sliding masts. The method which he proposed 

 was to make the masts themselves conductors of electricity, 

 by incorporating with them, in a peculiar way, two laminae 

 of sheet-copper, uniting these with the metallic masses in 

 the hull by other laminae, and giving the whole a free com- 

 munication with the sea. This method was tried experi- 

 mentally, both on models and to a large extent in the navy 

 itself; and a Commission appointed to examine the result 

 reported themselves highly satisfied with Mr. Harris's plan, 

 and strongly recommended that it should be fully carried 

 out in the Navy. See Mr. Snow Harris's paper in Phil. 

 Mag. March 1841. 



(B.) p. 20. A new mode of producing electricity has 

 excited much notice lately. In October, 1840, one of the 

 workmen in attendance upon a boiler belonging to the 

 Newcastle and Durham Railway, reported that the boiler 

 was full of fire ; the fact being, that when he placed his 

 hand near it an electrical spark was given out. This 

 drew the attention of Mr. Armstrong and Mr. Pattin- 

 son, who made the circumstance publicly known. (Phil. 

 Mag. Oct. 1840.) Mr. Armstrong pursued the investiga- 

 tion with great zeal, and after various conjectures was able 

 to announce (Phil. Mag. Jan. 1842, dated Dec. 9, 1841,) 

 that the electricity was excited at the point where the 

 steam is subject to friction in its emission. He found too 

 that he could produce a like effect by the emission of 

 condensed air. Following out his views, he was able to 

 construct, for the Polytechnic Institution in London, a 

 " Hydro-electric Machine," of greater power than any 

 electrical machine previously made. Dr. Faraday took up 



