[38] Not only at London, but at Paris, Vienna, Berlin, Turin. St. Petersburg, and almost every other capital in Europe; at Liege, Caen, Montpellier, Toulouse, and several other large towns,--wherever, in fact, there are not great local obstacles,--the tendency of the wealthier inhabitants to group themselves to the west is as strongly marked as in the British metropolis. At Pompeii, and other ancient towns, the same thing maybe noticed; and where the local configuration of the town necessitates an increase in a different direction, the moment the obstacle ceases houses spread towards the west. [39] By far the most complete set of experiments on the Radiation of Heat from the Earth’s Surface at Night which have been published since Dr. Wells’s Memoir _On Dew_, are those of Mr. Glaisher, F.R.S., _Philos. Trans._ for 1847. [40] The author is largely indebted for the illustrations in this new field of research to Lieutenant Maury’s valuable work, _The Physical Geography of the Sea_. Sixth edition. Harper, New York; Low, Son, and Co., London. [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._