Page:Popular Science Monthly Volume 3.djvu/370

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"I could wish," he says (I follow Ferguson's translation), "that many observations of the same phenomenon might be taken by different persons at several places, both that we might arrive at a greater degree of certainty by their agreement, and also lest any single observer should be deprived by the intervention of clouds of a sight which I know not whether any man living in this or the next age will ever see again, and on which depends the certain and adequate solution of a problem the most noble, and at any other time not to be attained to. I recommend it, therefore, again and again to those curious astronomers who (when I am dead) will have an opportunity of observing these things, that they would remember this my admonition, and diligently apply themselves with all their might to the making this observation; and I earnestly wish them all imaginable success; in the first place, that they may not, by the unseasonable obscurity of a cloudy sky, be deprived of this most desirable sight; and then that, having ascertained with more exactness the magnitudes of the planetary orbits, it may redound to their immortal fame and glory."

A few years before the transit of 1761, Delisle, the French astronomer, undertook a careful analysis of all the circumstances of the approaching phenomenon. It had been ascertained that the transit of 1761 was only the first of a pair of transits, the second occurring in 1769; and it was found that the method by which Halley had proposed to utilize the earlier transit would not, on this occasion, be altogether suitable. I shall presently describe the methods respectively suggested, but it is necessary to mention them here, in order that the chronological sequence of the events may be recognized. For many who have heard Delisle's method lately spoken of and insisted upon (as in Parliament by Mr. Goschen) have been led to imagine that it is a recent invention, and, again, that it possesses great advantages over Halley's, whereas it was known and discussed before the transits of 1761 and 1769, and, while very properly adopted for the first transit, was as properly superseded by Halley's in the case of the second.

The transit of 1761 (like that which will occur on December 6, 1882) was partially visible in England. It was observed at Greenwich by the Rev. M. Bliss, Astronomer Royal, and at Savile House, near London, by Mr. Short, "in presence," says the account, "of his Royal Highness the Duke of York, accompanied by their Royal Highnesses Prince William, Prince Henry, and Prince Frederick." A great number of observations[1] were made also in different parts of the world, and a sufficiently satisfactory determination of the sun's distance was deduced therefrom.

It was, however, in 1769, that the real attack was made. It was then that the famous expedition of Captain Cook, in the Endeavor, was made, England being the only country which had a station in the Pacific. The arctic regions were visited also, a station being selected at Wardhus, in North Lapland, where the following notable peculiar-

  1. There were 68 observing-stations in all, thus distributed: 13 in North Europe, 8 in England, 15 in France, 6 in Spain, Portugal, and Italy, 16 in Germany, and 3 in other places.