2 Electro-Magnetic Machine. 



statements of successful experiments at the late meeting at Bristol. 

 Mr. Sturgeon, of Woolwich, England, also reports a galvanic ma- 

 chine as being in use on his premises for pumping water, and for 

 other mechanical purposes.* 



But, I believe that Mr. Davenport, named at the head of this no- 

 tice, has been more successful than any other person in the dis- 

 coveryf of a galvanic machine of great simplicity and efSciency. 

 During the last two or three years, much has been said of this dis- 

 covery in the newspapers, and it is probable, that in a future number 

 of this Journal, drawings and an accurate description of the machine 

 may be given. Having been recently invited to examine a working 

 model, in two varieties of form, and to report the result, I shall now 

 attempt nothing more than a general description, such as may render 

 intelligible the account I am to give. 



1. The Rotary Machine, composed of revolving electro-magnets^ 

 with fixed 'permanent magnets. 



This machine was brought to New Haven March 16, 1837, by 

 Mr. Israel Slade, of Troy, N. Y., and by him set in motion for my 

 examination. The moving part is composed of two iron bars placed 

 horizontally, and crossing each other at right angles. They are both 

 five and a half inches long, and they are terminated at each end by 

 a segment of a circle made of soft iron ; these segments are each 

 three inches long in the chord line, and their position, as they are 

 suspended upon the ends of the iron bars, is horizontal. 



This iron cross is sustained by a vertical axis, standing with its 

 pivot in a socket, and admitting of easy rotation. The iron cross 

 bars are wound with copper wire, covered by cotton, and they are 

 made to form, at pleasure, a proper connexion with a small circular 

 battery, made of concentric cylinders of copper and zinc, which can 

 be immersed in a quart of acidulated water. Two semicircles of 

 strongly magnetized steel form an entire circle, interrupted only at 

 the two opposite poles, and within this circle, which lies horizontally, 

 the galvanized iron cross moves in such a manner that its iron seg- 

 ments revolve parallel and very near to the magnetic circle, and in the 

 same plane. Its axis at its upper end, is fitted by a horizontal cog- 

 wheel to another and larger vertical wheel, to whose horizontal axis, 



* Sturgeon's Annals of Electricity, Magnetism, &c. No. 1, Vol. 1. October, 

 1886. 



t Mr. Davenport appears to have been strictly the inventor of a method of ap- 

 plying galvanism to produce rotary motion. 



