216 ANNUAL OF SCIENTIFIC DISCOVERY. 



age. The crystal could in this way be cloven into an indefinite num- 

 ber of magnetic layers ; these layers set from pole to pole, and hence 

 the longest dimension, which was perpendicular to the layers. Com- 

 paring all these experiments ascending from the gross place where 

 the laminae were plates of iron stuck together by wax, to that in 

 which they were crystalline, the inference appears unavoidable, that 

 the unanimity of deportment exhibited, is the product of a common 

 cause ; and that the results are due to the peculiarities of a material 

 aggregation. 



The beautiful researches of Plucker in this domain of science are 

 well known. Plucker's first experiment was made with a plate of 

 tourmaline. Suspended in the magnetic field with the axis of the 

 crystal vertical, it set its length from pole to pole, like an ordinary 

 magnetic body. Suspended with the axis horizontal, on exciting 

 the magnet, Plucker found to his astonishment that the largest di- 

 mension set equatorial. Let us see if we cannot obtain this deport- 

 ment otherwise. Suspending the piece of shale already made use of, 

 so that its laminae were horizontal, on exciting the magnet the longest 

 horizontal dimension of the plate set axial ; moving the point of sus- 

 pension 90 so that the laminae were vertical, on exciting the magnet 

 the length of the plate set equatorial. In the magnetic field the de- 

 portment of the crystal was perfectly undistinguishable from that of 

 the shale. But it may be retorted that tourmaline possesses no such 

 laminae as those possessed by the shale ; true nor is it necessary that 

 it should do so. A number of plates, bars, and discs, formed arti- 

 ficially from magnetic dust, exhibited a deportment precisely similar 

 to the tourmaline, suspended from one point they set their lengths 

 axial, suspended from another point the lengths set equatorial. Let 

 us now turn to what may be called the complementary actions exhibit- 

 ed by diamagnetic bodies. A homogeneous diamagnetic bar sets its 

 length equatorial. But bars were exhibited composed of transverse 

 diamagnetic laminre which set their lengths axial. This experiment 

 is complementary to that of the shale, &c ; the magnetic laminaa set 

 axial, the diamagnetic equatorial; and by attention to this the mag- 

 netic body is made to behave like a homogeneous di;miagnetic body, 

 and the diamagnetic body like a homogeneous body. Diamagnetic bars 

 and discs were also examined, and a deportment precisely comple- 

 mentary to that of the magnetic bars and discs was exhibited. A mag- 

 netic disc sets its thickness from pole to pole and consequently its 

 horizontal diameter equatorial ; a diamagnetic disc sets its thickness 

 equatorial and its horizontal diameter from pole to pole. Two bodies 

 of the same exterior form and of the same color, were suspended 

 simultaneously in the fields of two electro-magnets, and both the latter 

 were excited by the same current ; the eye could detect no difference 

 of deportment. Both bodies possessed the shape of calcareous spar, 

 and both set the crystalographic axis equatorial. One body, however, 

 was composed of wax, while the other was a true crystal. In the 

 same way a crystal of carbonate of iron exhibited a deportment pre- 

 cisely the same as that o*f a model formed of magnetic dust. The ex- 



