Intelligence and Miscellaneous Articles. 11 



to 2*169 kilogrammes ; (2) the results found for ten simple mag- 

 nets made of other sorts of steel by M. van Wetteren, or made of 

 unknown kinds by Haeeker, Wenkebach, and Van Malderen, all 

 therefore more or less different from the first, and of weights vary- 

 ing from 0*492 to 3*033 kilogrammes. Formulae I. and II. being 

 judged applicable to compound magnets, I have given (3) the results 

 which I found for ten magnets of M. van Wetteren, each composed 

 of three plates — with the exception of one, which consists of five — 

 their weights varying from 1*411 to 3*707 kilogrammes. Sixteen of 

 Van Wetteren's simple magnets gave, on the average, A=0*89, and 

 B=0*89, the weights being expressed in kilogrammes, and the di- 

 mensions incentims.; the other ten simple magnets gave A=0*.88, 

 and B=0*88; and the ten compound magnets gave A=0*88, 

 B = 0*85. These thirty-six magnets, simple and compound, render 

 it probable that I. is the general empiric formula for the state of 

 supersaturation * in like manner, II. is the probable formula for 

 the state of permanence of simple magnets, while for them A=B. 

 The deviation of the value of B for the compound magnets seems 

 to me proved by the difficulties I experienced in the determination 

 of the position of the maxima of the intensity-curve. We shall 

 thus have 



P=A.Ov^/X, 



V Vs 



a formula to which, for simple magnets, the following is to be added, 



*= p (t)* Cm-) 



as I have said above ; while new observations will probably extend 

 formula III. to the compound magnets, which till then will be cha- 

 racterized by I. and II. 



I have already investigated the moments of free magnetism of 

 several of these simple magnets, in the open as well as in the 

 closed state of supersaturation and of permanence, by the devia- 

 tions they produce in a compass-needle. By supposing that the 

 tangents of these deviations, for one and the same magnet placed 

 at the same distance from the compass, are nearly proportional to 

 these moments, since the lever-arms of the moments are nearly 

 equal, I have obtained by these tangents an approximate measure 

 of the free magnetism in these three cases — that is to say, of the 

 integral of the intensity-curve (1) for the magnet open, (2) for 

 the magnet closed and supersaturated, and (3) for the closed 

 magnet reduced to permanence. 



In general the free magnetism for the magnet closed and super- 

 saturated is less than for the magnet closed and permanent ; the 

 free magnetism, in the closed and permanent state, is to the 

 magnetism in the open state nearly as 3 to 10, a proportion which 

 becomes more and more constant as the magnet approaches defini- 

 tive permanence by successive separations of the armature. This 

 slowly progressive march toward definitive permanence, announced 

 by a slight rise of the given proportion, can be traced in another 



