^{page 2 note *} Edinburgh Transactions, vol. xii. p. 1.—See also the Observations of Professor Bache; American Phil. Trans, vol. v.

^{page 2 note †} I cannot answer, however, for two or three of the first observations hereafter to be quoted.

^{page 2 note ‡} As the torsion of the silk fibre must have some influence, it is not unimportant to remark, that the same thread which was adapted to the instrument in August 1832, has been used ever since.

^{page 4 note *} None but those who have been engaged in observations of the very same description, where the eye, the ear, and the memory are all actively employed, can have an idea of the difficulty of always finding sites free from the interruptions of curiosity, or natural obstacles.

^{page 8 note *} My friend Professor Necker of Geneva has pointed out to me one of the first recorded observations of the influence of the aurora upon the magnetic needle, the more interesting because the coincidence was unnoticed (apparently) by the observer himself. In Saussure's, Voyages dans les Alpes, vol. iv. p. 300,Google Scholar that enterprising traveller notices an auroral appearance, observed from the Col du Geant on the 12th July 1788, and in another part of the same volume (p. 308), records, amongst his magnetical observations, the unsettled state of the needle during the whole of that evening.

^{page 9 note *} The mutual action of the needles is a point of importance. Before they came into my possession they were kept in their separate cases, but without farther attention, being packed together in the same external case in which they came from Norway. This arrangement I have not changed, but in packing them I have taken pains to place the opposite poles nearest one another, an arrangement which seems to have been attended with good effect; and to shew that needles may lie within an inch or two of one another without material injury, when we see the stationary condition of No. 1, and the diminishing rate of variation of the “Flat” Needle.

^{page 10 note *} Deduced from the measure of total intensity 1.3482 at Paris, given in the Mémoirés d'Arceuil, torn. i. multiplied by the cosine of the dip (there also given) 69° 12'.

^{page 13 note *} Many of the numerical calculations contained in the remainder of this paper, have been made by two of my pupils Messrs Irvine and Edward, under my own inspection and revision.

^{page 17 note *} It would be absurd to claim any merit for the application of a method so universally known. But lest I should be supposed to have borrowed without acknowledgment the method of reduction employed by Professor Lloyd and Captain Sabine in their excellent Magnetic Survey of Ireland (Fifth Report of the British Association), I desire to state, that I had some years ago proposed to myself the present method of reduction as the only one adapted finally to solve (within the present limits of error) the question of the influence of height, which so greatly complicates the problem.

^{page 19 note *} Since this paper was read, this result has been still more nearly confirmed by the observations of Professor Bache of Philadelphia, who, by connecting Edinburgh and Dublin, and talking Professor Lloyd and Captain Sabine's observations for the comparative intensities at Dublin and Paris, has obtained the number .8400.

^{page 19 note †} See his two papers in the Mémoires de l'Academie de Bruxelks, tome iv.; and an abstract in the Annuaire de l'Observatoire de Bruxelles, 1834.

^{page 21 note *} The intensity varies .01 for 27'5 of latitude.

^{page 22 note *} Since this passage was written, on mentioning to Professor Necker of Geneva, the anomalous result as to the direction of the isodynamic lines in the Pyrenees (anomalous, because differing from the supposed direction inserted in Hansteen's maps, which is deduced from analogy, and not, I believe, from direct observations in that country), he pointed out the curious (though perhaps accidental) coincidence which this result offers to the views he has long entertained as to the general parallelism of the lines of geological elevation, and those of magnetical intensity, which the bearing of the isodynamic lines which I have given for the Alps remarkably confirms.

^{page 22 note †} Saussure, Voyages aux Alpes, § 2103. Tom iv.

^{page 23 note *} See the details of the Observations in the Annales de Chimie. An. xiii. (1805), Tom. lii. p. 75.

^{page 23 note †} Tom. i. p. 1.

^{page 23 note ‡} Ibid. p. 10.

^{page 23 note §} The observations were not made at the summit of Mont Elbrouz, as stated in the Annuaire du Bureau des Longitudes, 1836, p. 288, but near the foot of it, and the difference of height of the stations was less than 5000 English feet. The stations were “Pont de Malka,” and “Hauteur de Kharbis.”

^{page 24 note *} Voyage, p. 39.

^{page 24 note †} P. 39, p. 44, p. 55.

^{page 24 note ‡} P. 44. p. 61, p. 65.

^{page 24 note §} P. 60, p. 66.

^{page 24 note ∥} P. 63.

^{page 24 note ¶} P. 65.

^{page 24 note **} P. 35.

^{page 28 note *} The coefficient ought to have been 28.

^{page 28 note †} This observation is certainly erroneous, and should have been discarded.