4 Electro-Magnetic Machine, 



and of course llieir relative energy, may be permanently supported, 

 and even carried to an extent much greater than has been hitherto 

 attained. 



2. Rotating Machine, composed entirely of electro-magnets, both 

 in its fixed and revolving members. 



A machine of this construction has been, this day, March 29, 

 1837, exhibited to me by Mr. Thomas Davenport himself, who came 

 from New York to New Haven for that purpose. 



It is the same machine that has been already described, except 

 that the exterior fixed circle is now composed entirely of electro- 

 magnets. 



The entire apparatus is therefore constructed of soft unmagnetic 

 iron, which being properly wound with insulated copper wire, is mag- 

 netized in an instant, by the power of a very small battery. 



The machine is indeed the identical one used before, except that 

 the exterior circle of permanent magnets is removed and in its place 

 is arranged a circle of soft iron, divided into two portions to form 

 the poles. 



These semicircles are made of hoop iron, one inch in width, and 

 one eighth of an inch in thickness. They are wound with copper 

 wire insulated by cotton — covering about ten inches in length on each 

 semicircle and returning upon itself, by a double winding, so as to 

 form two layers of wire, making on both semicircles about one thou- 

 sand and five hundred inches. 



The iron was not wound over the entire length, of one of the steel 

 semicircles ; but both ends were left projecting, and being turned in- 

 ward, were made to conform to the bend of the other __ 



... -i#^^ 



part, as in the annexed figure, which is intended to J^'y ' 



represent one of them ; each end that is turned inward 

 and not wound is about one third of the length of the semicircle. 

 These semicircles being thus fitted up, so as to become, at pleasure, 

 galvanic magnets, were placed in the same machine that has been 

 already described, and occupied the same place that the permanent 

 steel magnets did before. The conducting wires were so arranged, 

 that the same current that charged the magnets of the motive wheel, 

 charged the stationary ones, placed around it, only one battery being 

 used. It should be observed, that the stationary galvanic magnets 

 thus substituted for the permanent steel ones, were only about half 

 the weight of the steel magnets. This modification of the galvanic 

 magnet, is not of course the best form for efl^ciency ; this was used 



