]ME. C. V. WALKEE ON MAGNETIC STOEMS AND EAETH-CUEEENTS. 101 
general character of earth-currents; and of these I should be somewhat disposed to think 
that the observations made on September 7 are the most characteristic. Be this as it 
may, it comes out, from what we have recorded, that there is little difference of behaviour 
between the two kinds of currents. The S. currents, for instance, differ but little either 
in degree or in duration from the N. cm’rents. 
It is not my purpose in this communication to set forth any theory as to the origin 
of the currents in question; neither is it my object to discuss the auroral theories. But 
there is a certain feature in M. De la Rive’s theory which fails in the presence of the 
facts before us, and which requires notice here from the confidence with which it is put 
forth. On the faith of a few observations made on the Berne — Zurich telegraph line 
between 8*^ and 9'’a.m. on September 2, 1869, this philosopher arrives at the conclusion 
that the N. cmrents have a longer duration and are more powerful than the S. currents, 
and that the latter are merely due to the secondary polarities acquired by the earth- 
plates when they have transmitted a derived N. current. He calls the N. the direct 
current ; and he says, “ Nous pouvons done conclure de la, d’abord que le courant 
qui a la fois est le plus fort et dure le plus longtemps, est bien le courant direct pergu 
par le fil telegraphique, dont une des extremites plonge a Zurich dans le sol, et I’autre 
a Berne, et qu’il chemine bien du nord au midi, e’est a dire du pole nord a I’equateur ; 
nous sommes egalement condrdts a regarder le courant inverse de moindre intensite et 
de moindre duree, comme provenant des polarites secondaires qu’acquierent les deux 
lames de cuh-re plongees dans le sol, quand elles ont transmis dans un circuit ferme, 
pendant quelques instants, une derivation du courant terrestre. Ces deux conclusions 
.... sont, comme on le comprend, tres precieuses pour la theorie, et elles confirment 
pleinement celle que j’ai donnee dans ma premiere notice.” Further on he adds, “En 
effet il n’y a veiitablement dans le sol, lors de I’apparition de I’aurore, que des courants 
diriges du nord au sud ; ces courants sont seulement d’une intensite variable d’un instant 
a I’autre. Quant aux courants inverses plus faibles, et d’une duree moindre, qu’indiquent 
les appareils, ils ne sont que I’effet de la maniere dont on per^oit les premiers; les 
plaques de cuivre qui terminent les fils telegraphiques, et qui, plongees dans le sol 
seiwent de sondes pour deriver une portion des courants terrestres diriges du nord au 
sud, se polarisent bien vite, et donnent arnsi naissance a des courants inverses par I’effet 
des polarites secondaires qu’elles ontacquises*.” 
But from the figures before us it would be hard to say that either the N. or the S. 
current exceeds the other, either in value or in duration. Take for instance the high 
values, those exceeding 60°: if we have two N. currents between 61° and 65°, we have 
also two S. ; the same is the case between 66° and 70°, and 71° and 75°. And with 
respect to duration, the N. currents on some days, and the S. currents on others, have 
a total excess in time ; and if, on the one hand, the mean duration of each S. current is 
0’09 minute less than that of the N. currents, the total flow of S. currents is 21. minutes 
greater. Were it otherwise, it would still be impossible to admit a polarization of elec- 
* Arch, des Sc. Phys., Nouvelle periode, tom. vi. pp. 281, 282, 286. 1859, Nov. 20. 
