- 437 — 



tare in the annual variation than similarity of character and numerical 

 ■valne. At all the stations the solsiices are the turning- pcfiods of the an- 

 nucl variation at the hour of which we are treating, — the only periods 

 of the year in which the diurnal or horary variation at that hour does 

 actually disappear ara at the equinoxes, when the Sun is passing froni 

 the one hemisphere to the other, and when the mag-nelic direction, in 

 the course of its annual variation from east to west, or vice versa, coin- 

 cides with the direction which is the mean declination of all the months 

 and of all the hours — the annual variation is obviously connected with 

 and dependent on the Earth's position in its orbit relatively to the Sun, 

 around which is revolves; as the diurnal variation is connected with and 

 dependent on the relation of the Eartli on its axis, by which each meri- 

 dian succesively passes through every ang-le of inclination to the San 

 in the round of 24 hours.» (Sabine, on the annual and diurnal Variaiions, 

 en el 2.'' tomo aun idédito de Observations at Toronto, p. xvii-xx. Véase 

 también la Memoria del mismo sabio on the annual Variation of the mag- 

 netic Declination at dtfferenf periods o f the Day, en las Philos. Transactions 

 fnr 1851, 2.^ parle, p. 63o, y la introducción á las Observations at Hobar- 

 íon, t. I, p. xxxiv-xxxvi. 



(98) Pág-. 76.— Sabine, on the means adopted for determining the abso- 

 luta valúes, secular change and annual variation of the terrestrial magnetic 

 Forcé, en las Philosoph. Transactions for 18o0, 1.* parte, p. 216. Se lee 

 ademas en el Discurso de apertura pronunciado por Sabine en la Asam- 

 blea de BoMdiSi {Meeting of the British Association in 1832): «It is a rcmar- 

 kable fact which has been established, that the magnetic forcé is grea - 

 ter, in both the northern and southern liemispheres, in the months of 

 December, January and February, when the Sun is nearest to the Earth, 

 than in those of May, June and July, when he is most distant from it: 

 whereas, if the effects were due to íemperature, the two hemisphercs 

 should be oppositely instead of similarly affected in each of the two 

 periods referred to.» 



(99) Pág. 76. — Lamont, en los Annalen de Poggendorff, t. LXXXIV, 

 p.S79. 



(100) Pag. 76. — Sabine, on periodical laws discoverable in the mean ef- 

 fects of the larger magnetic Disturbances, en las Philosoph. Transactions for 

 1852, 1.a parte, p. 121. Véase también Cosmos, t IV, p. 69, n.'' 9. 



(1) Pág. 77. -Cosmos, t. líl, p. 869. 



(2) Pág. 77. — Cosmos, t. III, p. 157 



(3) Pág. 77. — Kreil, Einfluss des Mondes auf diemagnetische Declination, 

 Í8r>2,p. 27, 29 y 46. 



