There will not be another transit of Venus over the Sun’s disk, until the 8th of December, 1874; which, it is probable few persons now living will have an opportunity of observing, astronomically: And from that time, down to the 14th of June, A. D. 2984, inclusively,—a period of upwards of eleven centuries,—the same planet will pass over the Sun only eighteen times. There will be one other such transit of this planet, within the present century; after which there will not be another, during the term of one hundred and twenty-one years and an half. [See Table of the Transits of Venus over the Sun, in Lalande’s _Astronomie_; vol. ii.] ----- As the time approached near, when this extraordinary and almost unprecedented[109] astronomical phænomenon was to manifest itself, the public expectation and anxiety, which were before considerable, became greatly heightened. The ignorant—and those, generally, unacquainted with the nature of the looked-for event,—hearing much every where said on the subject, and seeing the preparations making for the occasion, had their curiosity wonderfully excited. To scientific men, the inestimable value of the approaching phænomenon suggested very different sensations. “Its importance to the interests of Astronomy and Navigation, had,” as Dr. Ewing observed at the time, “justly drawn the attention of every civilized nation in the world.” An accurate ascertainment of the Sun’s Parallax,—an important. and fundamental article in Astronomy, was a _desideratum_ not yet obtained. Only two Transits of Venus over the Sun, had been _observed_, prior to the 3d of June, 1769, since the creation of the world; and of these, the first alone was seen but by two persons:[110] Yet, as the learned gentleman just quoted has remarked,—“the Transits of Venus, alone, afford an opportunity of determining this problem” (the settling the Parallax of the Sun,) “with sufficient certainty: and these,” he adds, “happen so seldom, that there cannot be more than two in one century, and in some centuries none at all.” ----- Footnote 109: There had been but one of these transits of Venus over the Sun, during the course of about one hundred and thirty years preceding the transit of 1769; and, for upwards of seven centuries, antecedently to the commencement of that period, the same planet had passed over the Sun’s disk no more than thirteen times. [See Lalande’s Table, before referred to.] Footnote 110: Jeremiah Horrox and William Crabtree, two Englishmen, were the observers of the Transit of Venus of 1639. -----