Faraday on Electro-Magnetic Rotation. 291 



Philosophy, N. S. vols. \\. and III. Nearly the whole of that 

 sketch was written in the months of July, August, and Sep- 

 tember, of 1821 ; and the first parts, to which I shall particu- 

 larly refer, were published in September and October of the 

 same year. Although very imperfect, I endeavoured, as I think 

 appears on the face of the papers, as far as in me lay, to 

 make them give an accurate account of the state of that branch 

 of science. I referred, with great labour and fatigue, to the dif- 

 ferent journals in which papers by various philosophers had 

 appeared, and repeated almost all the experiments described. 



Now this sketch was written and published after I had heard 

 of Dr. Wollaston's expectations, and assisted at the experiments 

 before referred to ; and I may, therefore, refer to it as a public 

 testimony of the slate of my knowledge on the subject before 1 

 began my own experiments, I think any one, who reads it 

 attentively, will find, in every page of the first part of it, proofs 

 of my ignorance of Dr. Wollaston's views ; but 1 will refer 

 more particularly lo the paragraph which connects the 198th 

 and 199th pages, and especially to the 18th and 19th lines of 

 it ; and also to Fig. IV. of the accompanying plate. There is 

 there an eifect described in the most earnest and decided 

 manner, (see the next paragraph but one to that referred to,) my 

 accuracy, and even my ability, is pledged upon it ; and yet 

 Dr. Wollaston's views and reasonings, which it is said I knew, 

 are founded, and were, from the first, as I now understand, upon 

 the knowledge of an effect quite the reverse of that I have stated. 

 I describe a neutral position when the needle is opposite to the 

 wire ; Dr. Wollaston had observed, from the first, that there was 

 no such thing as a neutral position, but that the needle passed 

 by the wire: I, throughout the sketch, describe attractive and 

 repulsive powers on each side the wire ; but what I thought 

 to be attraction to, and repulsion from the wire in August, 1821, 

 Dr. Wollaston long before perceived to arise from a power not 

 directed to or from the wire, but acting circumfercntially round 

 it as axis, and upon that knowledge founded his expectation. 



I have before said, I repeated most of the experiments de- 

 scribed in the papcis referred to in the sketch; and it was in 



