NATURAL PHILOSOPHY. 217 



planation of these phenomena may be given in a few -words. In the 

 construction of the models, the magnetic or diamagnetic dust Avas 

 formed into a kind of dough and pressed between t\vo glass plates ; 

 the same process was applied to the wax ; and it is a universal law, 

 that in diamagnetic bodies the line along which the density of the 

 mass has increased by compression, sets equatorial and in magnetic 

 bodies axial. A reference to this principle will instantly render plain 

 all the experiments we have described. In those cases where the 

 same artificial bar set at one time axial and at another time equatorial, 

 the deportment depended on the circumstance whether the line of 

 compression was vertical or horizontal. When vertical its directive 

 power was annulled, and the action was determined by the exterior 

 form of the body; but when horizontal, its directive action came into 

 play and determined the position of the mass. The magnetic bar, for 

 example, suspended with its line of pressure vertical, set axial, but 

 with its line of pressure horizontal, it set equatorial; for the pressure 

 was exerted at right angles to its length. This action is so general 

 that it is difficult to find a body so perfectly homogeneous as not to 

 exhibit it in some degree. Ipecacuanha lozenges and Carlisle biscuits 

 were suspended in the magnetic field, and exhibited a most striking 

 directive action. The materials in both cases were diamagnetic ; but 

 owing to the pressure exerted in their formation their largest horizon- 

 tal dimensions set from pole to pole, the line of compression being 

 equatorial. 



Let us endeavor to arrive at the precise logical import of these ex- 

 periments. Let us suppose that before ever a crystal had been sus- 

 pended in the magnetic field, we were acquainted with the fact that a 

 slight change of density in any direction is accompanied by such 

 modifications of the magnetic force as those above described: that 

 we know that flour, bran, soap, shale, magnetic dust, &c., all exhibited 

 this directive action, that it is, in fact, a universal law of matter; 

 and then let us imagine some fortunate experimenter hanging a crys- 

 tal between the poles and observing a deportment in every respect 

 similar. Would not the analogy of the case at once flash tfpon him ? 

 Would not he regard this deportment as a beautiful, but still special 

 example of that all-pervading law with which he was previously ac- 

 quainted ? Would he not congratulate himself on the possibility thus 

 opened to him of searching out the mysteries of crystalline structure, 

 and rendering apparent to his mental eye the manner in which the 

 molecules are affsrejjated together ? He would never have assumed 



oo o o 



the existence of forces altogether new to account for the observed ac- 

 tions ; much less would he have affirmed that they were wholly inde- 

 pendent of magnetism or diamagnetism, for he would know before- 

 hand that the modification of these forces by the peculiarities of 

 aggregation was the exact thing calculated to produce the phenomena. 

 But magnocrystallic action was discovered when its universality was 

 unknown ; and hence its discoverer was led to regard it as something 

 unique. A great temptation lay in his way ; years before, a magnet, 

 now present, had twisted a ray of light, and thus suggested a connex- 



