Researches in the Theory and Calculus of Operations. 287 



nate presentation and withdrawal of the meridians to and 

 from the rays of the San explains the daily variations of" 

 the needle, and at the same time may serve to recal the 

 image of the solenoid magnet formed by the spiral wire 

 surrounding its core of soft iron. Starting from a point in 

 the northern hemisphere and pursuing a southerly air line, 

 the traveller will not remain on his first meridian, but will 

 course a loxodromic curve, winding in dextral direction 

 and making western longitude. Similarly the annual ap- 

 proach and recession of the earth in its orbit with respect 

 to the sun has been regarded as explaining the needle's 

 annual variation. The preponderance of land to water in 

 the northern hemisphere when compared with the south- 

 ern, indicates a corresponding possession of a larger pro- 

 portion of the ferruginous element, at least sufficient to 

 account for the seeming superiority or priority of develop- 

 ment of the northern polar electricity over the southern. 

 The cause of magnetic storms is referable to disturbances 

 in the photosphere of the Sun, which alter its actinic and 

 calorific effects upon the superficies of the earth. The well 

 known luminous effect of an electric discharge through a 

 partial vacuum suggests the plausibility of the usual ex- 

 planation that the aroused demonstrations are owing to the 

 formation of a partially vacuous stratum in the higher 

 regions of the atmosphere, arising from a sudden fall of 

 temperature, itself probably the consequence of the solar 

 disturbances mentioned. 



25. The normally developed atoms, such as would be 

 produced by equal pressure applied on all sides, are doubt- 

 less of spherical form, the three mutually perpendicular 

 central axes of which would be the proper measures of the 

 emanating forces in those directions. But each denizen, 

 each body, each atom of this our ancient mother Earth is 

 simultaneously and incontinently invaded by three mutually 

 cross terrestrial or rather' cosmical forces, each unequal in 



