Page:Popular Science Monthly Volume 22.djvu/177

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This hourly current acts on the magnet which drops the Greenwich time-hall daily at one o'clock, and on the magnet of the hourly relay (to the left in Fig. 5) which completes several independent circuits, each controlling a separate line of wire. One of these extends to the central telegraph station at the General Post-Office in London, and another to the London Bridge Station of the Southeastern Railway. The hell and galvanometer marked in Fig. 5 "P. O. Telegraphs" and "S. E. R. Hourly Signal and Deal Ball" show the passage of these currents.

Thus far the service is under the control of the astronomer royal, and he holds himself responsible to send the signals described along each line every hour of the day and night with the greatest attainable accuracy. The signals are generally correct within one tenth of a second of error. Should, however, by any accident, an hourly signal be in error, even to half a second, another signal is immediately sent, announcing that the last was not reliable. Special pains are then taken that the next hourly signal be correct. Here the responsibility of the astronomer royal (except for the dropping of the Deal ball, to be explained later) ends.

On the other hand, it is to be remarked that the Post-Office Department, which undertakes the distribution of these signals to London and the country, agrees to furnish subscribers, not with correct signals, but with the signals which they receive from Greenwich. The Greenwich signals, however, being considered everywhere in England as absolutely correct, constitute a standard from which there is no appeal.

[To be continued.]


By T. STERRY HUNT, LL. D. (Cantab.), F. R. S.

THE occasion which brings us together is one which should mark a new departure in the intellectual history of Canada. Science and letters find but few votaries in a country like this, where the best energies of its thinkers are necessarily directed to devising means of subduing the wilderness, opening the ways of communication, improving agriculture, building up industries, and establishing upon a proper basis schools in which the youth of the country may be instructed in those arts and professions which are among the first needs of civilized society. The teachers, under such conditions, can do little

  1. The President's Address before the Mathematical, Physical, and Chemical Section of the Royal Society of Canada, at the first meeting of the society, Ottawa, May 27, 1382. Reprinted, with an added note, from the "Canadian Naturalist," vol. x, No. 5.