130 



FARMERS' liEGISTER, 



[No. 3 



operates with beautiful and surprising eflect, and 

 no reason can be discovered why the motion may 

 not be indefinitely continued. It is easy to cause 

 a very gradual flow of the impaired or exhausted 

 acid liquor from, and of fresh acidulated water 

 into, the receptacle of the battery, and whenever 

 the metal of the latter is too much corroded to be. 

 any longer efficient, another battery may be in- 

 stantly substituted, and that even before the con- 

 nexion of the old battery is broken. As to the 

 energy of the power, it becomes at once a most 

 interesting inquiry, whether it admits of indefinite 

 increase ? To this inquiry it may be replied, that 

 provided the magnetism of bolh the revolving 

 cross and of the fixed circle can be indefinitely in- 

 creased, then no reason appears why the ener- 

 gy of the power cannot also be indefinitely in- 

 creased. Now, as magnets ol" the common kind, 

 usually called permanent magnets, find their limits 

 within, at most, the power of lifting a iew hundred 

 pounds, it is obvious that the revolving galvanic 

 magnet must, in its efficiency, be limited by its 

 relation to the fixed magnet. But it is an impor- 

 tant fact, discovered by experience, that the latter 

 is soon impaired in its power by the influence of 

 the revolving galvanic magnet, which is easily 

 made to surpass it in energy, and thus, as it were, 

 to overpower it. It is obvious, therefore, that the 

 fixed magnet, as well as the revolving, ought to 

 be magnetized by galvanism, and then there is 

 every reason to believe that the relative equality of 

 the two, and of course their relative energy, ma}' be 

 ])ermanently supported, and even carried to an ex- 

 tent much greater than has been hitherto attained. 



2. Rotating 3Iachme, composed entirely of elcc- 

 tro-rnagnets, 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 himsellj who came from New 

 York to New Haven for that purpose. 



It is the same machine that has been already 

 described, except that the interior fixed circle is 

 now composed entirely of electro-magnets. 



The entire apparatus is theretbre constructed of 

 soft unrnagnetic iron, which being properly wound 

 with insulated copper wire, is magnetized in an 

 instant, by the power of a very small battery. 



The machine is indeed the identical one used 

 before, except that the interior 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 insu- 

 lated by cotton — covering about ten inches in length 

 on each semicircle and returning upon itselfj by a 

 double winding, so as to form two layers of wire, 

 making on both semicircles about one thousand 

 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 inward, were 

 made to conform to the bend of the other part; 

 [the turned ends being parallel and near to the in- 

 side of the bend ;] each end that is turned inward 

 and not wound, is about one thn-d of the length of 

 the semicircle. These semicircles being thus fit- 

 ted up, so as to become, at pleasure, fjalvanic mag- 

 nets, were placed in the same machine that has 

 been already described, and occupied Ihe 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 efnciency ; this was 

 used merely to try the principle, and this construc- 

 tion may be superseded by a dillierent and more 

 efficient one. But with this arrangement, and 

 notwithstanding the imperft;ction of the mechan- 

 ism of the machine — when the battery, requiring 

 about one quart of diluted acid to immerse it, was 

 attached, it lifted 16 lbs. very rapidly, and when 

 the weight was removed, it performed more than 

 600 revolutions per minute. 



So sensible was the machine to the magnetic 

 power, that the immersion of the battery one inch 

 into the acidulated water, was sufilcient to give it 

 rapid motion, which attained its maximum when 

 the battery was entirely immersed. It appeared 

 to me that the machine had more energy with the 

 electro-magnets, than with those that were per- 

 manent, for with the smallest battery, whose di- 

 ameter was three inches and a halfj its height 

 five inches and a half, and the number of con- 

 centric cylinders three of copper and three of 

 zinc, the instrument manifested as great power 

 as It had done with the largest batteries, and even 

 with a large calorimotor, when it was used with a 

 permanent instead of a galvanic magnet. With 

 the small battery and with none but electro or gal- 

 vanic magnets, it revolved with so much energy 

 as to produce a brisk breeze, and powerfully to 

 shake a large table on which the apparatus stood. 



Although the magnetization of both the station- 

 ary and revolving magnets was imparted by one 

 and the same battery, the magnetic power was not 

 immediately destroyed by breaking the connexion 

 between the battery and the stationary magnet ; 

 for, when this was done, the machine still per- 

 formed its revolutions with great although dimin- 

 ished energy ; in practice this might be important, 

 as it would give time to make changes in the appa- 

 ratus, without stopping the movement of the ma- 

 chine. 



It has been stated by Dr. Ritchie, in a late 

 number* of the London and Edinb. Phil. Maga- 

 zine, that electro-magnets do not attract at so 

 great a distance as permanent ones, and therefore 

 are not well adapted for producing motion. On 

 this point Mr. Davenport made the following ex- 

 periment, of which I was not a witness, but to 

 which I gave full credit, as it was reported to me 

 by Mr. Slade, in a letter dated New York, March 

 2i, 1837. 



Mr. Davenport suspended a piece of soft iron 

 with a long piece of twine, and brought one pole 

 of a highly charged steel magnet within the at- 

 tracting distance, that is, the distance at which 

 the iron was attracted to the magnet ; by measure- 

 ment, it was found that the steel magnet attracted 

 the iron one inch and one fourth. A galvanic mag- 

 net was next used of the same lifting power, and 

 consequently of much less weight ; the attracting 

 distance of this magnet was found to be one inch 

 and three fijurths, showing a material gain in fii- 



January, 1837. 



