NATURAL, PHILOSOPHY. 133 



same law, with the exception that the maxima of the one element oc- 

 cur at the same hours as the minima of the other. 3. The observed 

 variations of the horizontal magnetic intensity are legitimate conse- 

 quences of the thermal theory of terrestrial magnetism ; granting that 

 moisture has a magnetic action. 4. The deviations in the variations 

 of the horizontal force from the law of proportionality to temperature, 

 are caused by the deposition of vapor from the atmosphere, and its 

 evaporation from the earth's surface. 5. The diurnal variations of the 

 vertical magnetic intensity are for the most part in accordance with 

 the idea that they arise from variations in the difference between the 

 temperature at the station of the needle and that at a place north or 

 south of it. 6. The connection between the diurnal variations of the 

 declination and those of the horizontal force, which is undoubted, may 

 be described as follows : When the curve showing the diurnal vari- 

 ations of the horizontal force is concave upward, the declination (west- 

 erly) is increasing ; when convex upward, it is decreasing. Conse- 

 quently the maxima and minima of declination must be contemporane- 

 ous with the points of inflection of the curve of horizontal force. 

 7. The annual variations of declination appear to be mainly depen- 

 dent upon an annual oscillatory movement of the isothermal line. 



OXYGEN MAGNETIC. 



THE Bakerian lecture was delivered on Nov. 28, by Prof. Faraday. 

 We can now only glance at the highly interesting investigations laid 

 before the Royal Society. One of the conclusions arrived at was, that 

 the motions of magnetic and diamagnetic bodies toward each other do 

 not appear to resemble those of attraction or repulsion of the ordinary 

 kind, but to be of a differential action, dependent perhaps upon the 

 manner in which the lines of magnetic force were affected in passing 

 from one to the other during their course from pole to pole, the differ- 

 ential action being in ordinary cases between the body experimented 

 with and the medium surrounding it and the poles. A method of 

 showing this action with the gases is described, in which delicate soap- 

 bubbles are made to contain a given gas, and then, when held in the 

 magnetic field, approach, or are driven further off, according as they 

 contain gases magnetic or diamagnetic in relation to air. Oxygen 

 passes inwards or tends towards the magnetic axis. Perceiving that 

 if two like bubbles were set on opposite sides of a magnetic core or 

 keeper cut into the shape of an hour-glass, they would compensate 

 each other, both for their own diamagnetic matter and for the air which 

 they would virtually displace, and that only the contents of the bulbs 

 would be virtually in a differential relation to each other, the author 

 passed from bubbles of soapy water to others of glass ; and then con- 

 structed a differential torsion balance, to which these could be attached, 

 of the following nature : A horizontal lever was suspended by co- 

 coon silk, and at right angles to the end of one arm was attached a 

 horizontal cross-bar, on which, at about an inch and a half apart, and 

 equidistant from the horizontal lever, were suspended the glass bub- 

 bles ; and then the whole beino: adjusted so that one bubble should be 



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