[41] It is the chloride of magnesia which gives that damp sticky feeling to the clothes of sailors that are washed or wetted with salt water.
[42] This fraction rests on the assumption that the dilatation of the substances of which the earth is composed is equal to that of glass, that is to say, 1/18000 for 1°. Regarding this hypothesis, see Arago, in the Annuaire for 1834, pp. 177–190.
[43] Electricity, traversing excessively rarefied air or vapours, gives out light, and doubtless also heat. May not a continual current of electric matter be constantly circulating in the sun’s immediate neighbourhood, or traversing the planetary spaces, and exerting in the upper regions of its atmosphere those phenomena of which, on however diminutive a scale, we have yet an unequivocal manifestation in our Aurora Borealis?
[44] Could we by mechanical pressure force water into a solid state, an immense quantity of heat would be set free.
[45] See Mr. Hunt’s popular work, The Poetry of Science; or, Studies of Physical Phenomena of Nature. Third edition, revised and enlarged. Bohn, 1854.
[46] Canton was the first who in England verified Dr. Franklin’s idea of the similarity of lightning and the electric fluid, July 1752.
[47] This is mentioned in Procli Diadochi Paraphrasis Ptolem., 1635. (Delambre, Hist. de l’Astronomie ancienne.)
[48] The first Variation-Compass was constructed, before 1525, by an ingenious apothecary of Seville, Felisse Guillen. So earnest were the endeavours to learn more exactly the direction of the curves of magnetic declination, that in 1585 Juan Jayme sailed with Francisco Gali from Manilla to Acapulco, for the sole purpose of trying in the Pacific a declination instrument which he had invented.—Humboldt.
[49] Gilbert was surgeon to Queen Elizabeth and James I., and died in 1603. Whewell justly assigns him an important place among the “practical reformers of the physical sciences.” He adopted the Copernican doctrine, which Lord Bacon’s inferior aptitude for physical research led him to reject.
[50] This illustration, it will be seen, does not literally correspond with the details which precede it.