^{page 641 note *} These epochal waves of heat may apparently come to a head at any time in the course of a year; but are never so powerful as to destroy altogether the ordinary summer or winter. If therefore one, of any cycle, occur just at mid-winter, it merely makes it an unusually mild winter; not a season as hot as, or hotter than, an ordinary summer.

^{page 641 note †} These Sun-spots have been proved, by Professor Langley and others, to have no power in themselves to produce any notable alteration in the quantity of the Sun's radiant heat practically felt by the earth and its atmosphere; but bear about the same relation to it, that the cinders dropping into the ash-pit of a steam engine's fire-place, do to the amount of mechanical work being performed by the engine at the moment; and if the engine itself is not observable by us, it is well to note and reason on the number and size of the red-hot cinders, and the rate at which they fall.

^{page 643 note *} In MrChambers', George F.“Handbook of Astronomy,” 3d edition (Clarendon Press, Oxford)Google Scholar, there is an immense amount of well-collected, useful information, in the course of the first chapter, on the Sun-spots and their influence, first on the magnetism, and then on the Auroras of the weather of the earth, as determined by a positive crowd of first-rate and honourable observers, mathematicians, astronomers, and physicists.

Closely following on M. Schwabe's announcing the periodicity of Sun-spots, there were published in 1850 to 1852 a series of almost simultaneous but independent discoveries and demonstrations by Professors Lamont of Munich, Gautier of Geneva, Wolf of Zurich, and General Sabine of London, of the close connection between Sun-spots and the earth's changes of magnetism, so that, not only were the periods the same in the whole, but the maxima and minima were conformable also. While still more pointedly, when in 1859, a terrestrial magnetic storm of unprecedented magnitude occurred from August 28 to September 7, it was shown by Professor Stewart, Balfour (“Philosophical Transactions,” 1861, p. 423)Google Scholar, that this was synonymous with the period of maximum activity of one of the largest Sun-spots ever observed. (See a Physical Treatise on Electricity and Magnetism, by Gordon, J. E. H., B.A., 1880, vol. i. p. 197Google Scholar.)

Whereupon Mr Chambers quotes the shrewd and far-seeing Manchester scientist, Mr Baxendell, as considering,—“That diversities of solar activity are to be regarded as causing changes in the magnetic condition of the Earth, and so producing changes in the directions and velocities of the great currents of the atmosphere, and in the distribution of barometric pressure, temperature, and rainfall.” And he expressly lays down further on, that “the future progress of meteorology must depend, to a much greater extent than has generally been supposed, upon the knowledge we may obtain of the nature and extent of the changes which are constantly taking place on the surface of the Sun.”

Mr Chambers quotes also Professor Balfour Stewart for proving that a bond of connection exists between Sun-spots and these three terrestrial features—magnetic declination, “earth currents,” and Aurora; also Professor Loomis of America, as having well remarked through long periods, the connection between Sun-spots, magnetic declination and Aurora, and given an effective map of them.

Also M. Pöey, for the connection of tropical storms with the maxima of Sun-spots through more than a century.

Also Mr Elvirs of Canada, for connection between Cycles of Sun-spots and rainfall frequency.

Also the Oxford Observatory, for connection between Sun-spots and the mean direction of the wind; the westerly element increasing with the amount of spots.

Also Mr Stone, at the time Astronomer Royal at the Cape of Good Hope, and equally M. Abbé of Cincinnati, but then discussing Munich observations; for they were each led to a connection between Sun-spots and terrestrial temperature.

Again, since the date of 1872, Mr Norman Lockyer, F.R.S., Dr W. W. Hunter (Statistician General for India), Mr Meldrum of Mauritius Observatory, Professor Stanley Jevons of London University, and Professor Douglas Archibald have written so much both separately and combinedly on Sun-spots, Indian rainfalls, and Indian famines, ship assurances in the Tropics, and commercial panics, and become so widely approved therein, that I need only allude to them here by name. Though it has not been sufficiently brought out yet that Dr W. W. Hunter received, apparently, his earliest ideas on the subject somewhere in 1875, from Mr N. Pogson, Government Astronomer at Madras, who was then in rather low spirits because he was expecting a famine in the next year; and expressly, as he particularly explained, on account of the approach of the period of a minimum of Sun-spots; which famine did take place, and with all the disastrous consequences to life in India, and purse in Great Britain, which the daily papers have chronicled since, but Mr Pogson saw feelingly so long beforehand.

^{page 644 note *} The disturbance of the Earth's Magnetism appears to have been noticed the same night at Vienna and also at Lisbon; see “Nature,” p. 220, No. 558, vol. xxii. or for July 8, 1880.

^{page 644 note †} Sophus Tromholt, Professor of Mathematics.

^{page 644 note ‡} Some of these were closer than he was aware of, for on August 11 and 12, summer season though it was, the most magnificent of coloured Auroras were witnessed over a large part of England and Scotland, accompanied by the most violent magnetic storm that had been felt for many years (see “Nature,” p. 361, No. 564, vol. 12; Aug. 19, 1880); while the Mean Temperature of that month turned out higher than for any August (that of 1857 excepted) chronicled by the Meteorological Society of Scotland, September too followed, with the same temperature characteristic.—P. S., Oct. 1880.

^{page 646 note *} The lengths for the five principal thermometers as eventually constructed were, from the surface of the ground down to the centre of each bulb, t ¹ = 250 British inches ; t ² = 125; t ³ = 50 ; t ⁴ = 25 ; t ⁵ = 1; while above the surface of the ground every thermometer had 30 inches additional of scale length.