36 Mr. Harvey on the Effects of Magnetism 



which the attractive force acts, with relation to the balance, it 

 would seem reasonable to infer, that the induced magnetism of a 

 simple iron mass, ought to produce effects of an analogous kind ; 

 since the nature of the force is the same, and varies only in 

 degree. 



With this view of the subject, [I was induced, in the early part 

 of the year 1822, to undertake a course of experiments, in order to 

 determine the influence of unraagnetized iron on several good chro- 

 nometers; and that branch of the inquiry which relates to the 

 effects of a thirteen-inch iron shell, I now submit to the readers 

 of the Journal of Science*. 



The concentric circles NE. SW., Figs. 1, 2, §-c., Plate II, 

 represent a horizontal section of the iron sphere passing through 

 its centre, the diameter NS., being in the magnetic meridian. The 

 smaller circles A, B, C, D, E, are horizontal sections of the chro- 

 nometers, in the situations in which they were respectively placed 

 round the sphere ; those situated either above or below the hori- 

 zontal plane, being orthographically projected on it. The posi- 

 tions of the balances and main springs of the time-keepers, are 

 represented by the lesser circles marked B and S ; and by which 

 the positions of those important parts of each chronometer, with 

 respect to the attracting mass, may be clearly seen. Figs. 5 and 

 1 1 represent vertical sections passing through the centre of the 

 iron shell, and the centres of the chronometers A, B, and F, A, in 

 the direction of the magnetic meridian ; the centres of their faces 

 being also in the plane E, Q, the magnetic equator of the sphere. 

 In like manner, Figs. 6 and 12 exhibit sections at right angles to 

 the former, passing through the centre of the sphere, and the 

 centres of the time-keepers E, D, C, and C, B, D, E ; and dis- 

 closing the relative positions of tlieir balances and springs f. So 



• In two other papers, 1 propose to treat of the influence of re-magnetized 

 iron plates and iron bars, on the rates of chronometers. 



•J- It was found impossible to introduce all the positions of the balances and 

 springs of the different chronometers, represented in the different horizontal 

 sections, in the vertical sections, without several additional figures. Their 

 positions represented in the last-mentioned sections do not refer to either of the 

 horizontal sections in particular, but are merely introduced for illustrating 

 their situations vertically. 



