all of his construction, they were admitted to have been better than could have been obtained abroad. According to Smith, the committee trusted in this respect entirely to the extensive knowledge of Rittenhouse, and when he and the others arrived, two days before the transit, they had nothing to do but adjust the telescopes to their vision. A rainy day, even a passing cloud, would have made all the labor vain, but fortunately it happened to be perfectly clear. The previous anxiety, the sense of responsibility at the critical moment, the delight consequent upon the great success, constituted a sequence of emotions too exciting for the physically delicate Rittenhouse, and when the contact had ended he swooned away. The observations, according to the testimony of Maskelyne, the royal astronomer of England, were excellent and complete. Rittenhouse at once made calculations to determine the parallax of the sun, and gave them to Dr. Smith, who added his own and prepared a report to the society, which was printed in its proceedings; and so it happened that the first approximately accurate results in the measurement of the spheres were given to the world, not by the schooled and salaried astronomers who watched from the magnificent royal observatories of Europe, but by unpaid amateurs and devotees to science in the youthful province of Pennsylvania.
Said a learned English author: “There is not another society in the world that can boast of a member such as Mr. Rittenhouse, theorist enough to encounter the problem of determining from a few observations the orbit of a comet, and also mechanic enough to make with his own hands an equal-altitude instrument, a transit telescope, and a time-piece.”
In the year 1769 there was also a transit of Mercury, a phenomenon by no means so rare or of such moment as
