The Earth's Magnetism

Tho great phyaieal problem of terrestrial magnetism bas engaged tho attention of numci'ovfs physicists lately, and it is well known that several ingenious solutions of it liave boon propóunded. Professors AyrtQB and Perry lor example, conceived the happy tliought that thü earth was charged wlth static elcctricity, wliioh beïng eanied round on tho surface by the diurnal rotation, a:led like a eirculating cuvrent and magnetized the core. A severe blow was dealt to this hypothesis, however, by tho mathcmatic'al criticism of Professor Eowland, who pointed out that the surface charge required was competent lo send a spark from earth to ruoon. A ineoiy bascd npon tho existene of electric eurrents Üowing ia tho a'mosphere aroiind the earth was protnulgated lal er; and now, saya Eugineering, we have nnother supposifion, whioh has a botter claim to serióos attention than any of the rest, becaase it is sup])oricd by direct experiment. Starting from the idea of M. Edlund that au elcetrie cnrrent is reaüy an ether eurjsent Üowing in the circuit, and that electrostaüc effects are di'.e to rarefactions and condensatkms of the ether, M. Selim Lemstrom considered that he might prodfioe this ether current bjr meèhanical action. He thort)fore made a paper tube havïng two coacentric walk and mounted on an axle. A core of soft i ron was placed withiri the tube, and on rotating the latter the core was lound to be magnetic, asdemonstrated by two line astatic nct'dies, Iteversing the" rotation reversed tlie magnetic poles; and M. Lemstrom concludea that the relativo motion of the ether in the revolving tube and the stationair core was the cause of the poLarity. Il follows that if the tube be stalionary and the core revolved a similar effect will beproduced; and henee if a magnetic body like earth be rapidly cotated round its axis in an insulating medium like the air, it will exhibit magnetism. Pursuing this idea into mathematies, M. Lemstrom arrivés at an expression for the magnetic moment of the earth which agrees very well with tlie formula of Gauss. A French journal has published an articli; on the New York lire brigade in order to show the French how miserably is their own army of pompiei'S wiLh their buekets and toy hantl pumps. A group of rnombers of the French Booiete Protectrioe des Animaux have determined to establish a refuge for lost animáis. A considerable sum has already been subsoribed for this purpqse.