444? Mr. Faraday on the Magnetic Spark and Shock. 



for the differences in our results. It seems only possible to 

 account for it by some oversight in the calculations ; but 

 where it lies I am totally unable to say. I have given at large 

 the principles on which my calculations are founded, which, 

 I believe, are in a mathematical point of view correct. At 

 any rate the subject eminently deserves further inquiry, which 

 I hope and trust it may receive from those who are much 

 better qualified than myself to do justice to it. Professional 

 avocations have, indeed, hindered me from going into as ac- 

 curate an examination of it as I could wish, and will, I fear, 

 (for some time at least,) prevent me from entering upon a si- 

 milar repetition of those other highly interesting photometricat 

 researches, which relate to the reflection from metallic sur- 

 faces, in which Mr. Potter has found such curious anomalies. 

 These, however, are not so immediately connected with the 

 object 1 had in view, which chiefly refers to the controversy 

 in regard to the undulatory theory. The experiments, how- 

 ever, on reflection from glass at different incidences have a 

 stronger claim to attentive examination, as forming the basis 

 of the calculation in all the other instances. 

 Queen Street, Nov. 1, 1834. 



LXII. Additional Observations respecting the Magneto-electric 



Spark and Shock. By Michael Faraday, Esq., D.C.L., 



F.R.S., %c. 



To Richard Phillips, Esq., F.R.S., fyc. 

 My dear Sir, 

 IKE most things done in haste, my letter to you last 

 ■" month involves several errors, some from want of atten- 

 tion, others from want of knowledge. Will you do me the 

 favour to print the present in correction of them ? 



The first error consists in supposing the electricity of the 

 shock and the electricity of the spark (obtained at the moment 

 of disjunction) are due to different currents, page 351. They 

 are, as I find by careful experiments, due to the same current, 

 namely, one produced by an inductive action at the moment 

 when the current from the electromotor ceases. 



If at p. 351, line 26, after "set in motion" be inserted 

 " through the body;" and at line 31, for " counter" be read 

 " second ", and if the above statement be allowed to stand for 

 that at the top of page 352, this error will be corrected. 



The experimental results which I anticipated, page 352, 

 lines 31—35, and page 354, lines 26—32, do not occur ex- 

 cept under peculiar circumstances, and I am now aware why, 

 for natural reasons, they should not. All the effects, in fact, 



