1822.] of Magnetism to Iron in different Positions, 93 



abstract of which is also given in the Annah for May, 1821. 

 Among other interesting facts, he states, that iron may be ren- 

 dered magnetic by being bent, scowered, filed, or twisted, in the 

 position of the magnetic axis, or near it. He states, however, 

 nothing more with respect to the degree of magnetism communi- 

 cated at different inchnations ; it is to the determination of this 

 point that my inquiries have been directed ; and I conceive I 

 have discovered a simple law by which the increase of intensity 

 thus communicated is regulated, as the inclination varies from 

 the magnetic equator to the axis. I am not aware of any similar 

 law being given by other writers ; the paper above alluded to 

 being the only one I know of, which treats at all on this depart- 

 ment of the science of magnetism. 



The experiments which 1 have tried have been conducted in a 

 very simple manner ; pieces of iron wire, which were previously 

 found to have no magnetism, were fixed at different inchnations 

 to the magnetic equator (every 10th degree) ; assuming the dip 

 at 70° 30', according to Mr. Barlow's determination. The appa- 

 ratus was fixed in the j)lane of the magnetic meridian ; and the 

 wires being fixed firmly at one end were, by means of the other, 

 wrenched or twisted in such a way that they retained their recti- 

 linear form, and their position at the proper angle. The same 

 number of turns in wrenching was given to each piece ; and 

 when thus magnetized, their respective intensities were deter- 

 mined by comparing the deviations which they caused on a 

 light magnetic needle, care being taken that they were all placed 

 in a similar position and distance from the pole of the needle. I 

 selected six sets of experiments which I considered as most to 

 be depended on, the mean results of which are as follow : 



I 



It is obvious that the deviations do not diminish as the inchna- 

 tions ; I, therefore, after several trials, considered the following 

 law as giving a very near approximation to the above results. 



tan. D, a sin. I. D = deviation. I = inclination. 



This will be obvious by comparing the respective sines and 

 tangents ; which are : 



sin. I. 



an. D. 



10000000 



5000352 



9848078 



4913386 



9396926 



4698539 



8660294 



4296339 



7660444 



3872058 



6427876 



3217061 



5000000 



2539676 



3420201 

 1853390 



1736482 



0670043 



In the present experiments, the greatest deviation correspond- 

 ing to the inc. 90° was, for the sake of convenience of compa^ 



