". . . wrapped or wound round throughout its whole length, in silk thread. Thus 

 all electric communication is avoided between the different parts of this wire, the 

 turns of which are wound one over or above the other, as it is placed in the groove of 

 the frame." - 



Insulated wire had not been applied to magnets, they being con- 

 structed by insulating the magnet core and winding on it a single 

 spiral of uninsulated wire. The following is Henry's first description 

 of the application of insulated wire to magnets: 



"In a paper, published in the Transactions of the Albany Institute, June, 1828, I 

 described some modifications of apparatus, intended to supply this deficiency of Mr. 

 Sturgeon [weak magnetic effects], by introducing the spiral coil on the principle of the 

 galvanic multiplier of Prof. Schweigger, and this I think is applicable in every case 

 where strong magnets cannot be used. . . . Shortly after the publication mentioned, 

 several other applications of the coil, besides those described in that paper, were 

 made in order to increase the size of electro-magnetic apparatus, and to diminish the 

 necessary galvanic power. The most interesting of these, was its application to a 

 development of magnetism in soft iron, much more extensively, than to my knowledge 

 had been previously effected by a small galvanic element. 



"A round piece of iron, about 1/4 of an inch in diameter, was bent into the usual 

 form of a horse-shoe, and instead of loosely coiling around it a few feet of wire, as is 

 usually described, it was tightly wound with 35 feet of wire, covered with silk, so as 

 to form about 400 turns; . . . ." ^ 



The nearest approach which has been found to a contemporary 

 statement indicating possible anticipation by others is the following 

 published by Silliman in his journal for July, 1837: 



"Prof. Moll, of Utrecht, by winding insulated wire around soft iron, imparted to 

 it prodigious magnetic power, so that a horse shoe bar, thus provided, and connected 

 with a galvanic batter\-, would lift over one hundred pounds. About the same time, 

 Mr. Joseph Henr>', of Albany, now Prof. Henry, of Princeton College, by a new 

 method of winding the wire, obtained an almost incredible magnetic force. . . ." 



However, reference to Moll's own account of his work published in 

 the Edinburgh Journal of Science April-October, 1830, and copied in 

 Silliman'' s Journal for January, 1831, and to another contemporary 

 account of Moll's work gives no indication of his having used insulated 

 wire. 



Henry also used other insulating materials. In SW, \'ol. 1, p. 48 

 (1831), he acknowledged Dr. Beck's suggestion for using well waxed 

 cotton instead of silk thread and also mentioned Dr. Beck's experiments 

 with iron bonnet wire "which, being found in commerce already wound, 

 might possibly be substituted in place of copper. ..." 



In 1832 he described winding the armature of a magnet with "A 

 piece of copper wire, about thirty feet long and covered with elastic 

 varnish. ...""* In this, however, he was anticipated as to publication 



^ Electro- Magnetism etc., Jacob Green, 1827, pp. 81-83. 

 'SW,* Vol. 1, pp. 37-38; paper published January, 1831. 

 «SW, Vol. 1 p. 75. 



* Scientific Writings of Joseph Henry, published bv the Smithsonian Institution 

 in 1886. 



