Page:Popular Science Monthly Volume 36.djvu/857

Rh Some one having published the result of calculations he had made respecting the fulfillment of Archimedes's famous dictum on the subject, Mr. Rittenhouse gave the result of his own computations, which was that "the force wherewith a man acts when he lifts a weight of two hundred pounds, if applied without intermission for the space of one hundred and five years, is sufficient, without any machinery, to move the earth one inch in that time; and it must, from the velocity received by that force alone, continue forever after to move at the rate of one inch in fifty years." The first calculator had computed that twenty-seven billions of years would be required to accomplish the movement.

Mr. Rittenhouse's reputation as an astronomer became conspicuous, and his name, according to Mr. Barton, acquired a celebrity even in the Old World, "of which his early but now much-increased fame in his native country was a sure presage." A great bound was given to his fame by his construction of an orrery, or apparatus for illustrating the planetary motions, and by the conspicuous part which he took in the observations of the transit of Venus of 1769.

The design of the orrery is indicated in the correspondence with Mr. Barton in 1767, in the course of which Mr. Rittenhouse says: "I did not design a machine which should give the ignorant in astronomy a just view of the solar system; but would rather astonish the skillful and curious examiner by a most accurate correspondence between the situations and motions of our little representatives of the heavenly bodies and the situations and motions of those bodies themselves. I would have my orrery really useful by making it capable of informing us truly of astronomical phenomena for any particular point of time, which I do not find that any orrery yet made can do."

This instrument was bought before it was finished for Princeton College. The trustees of the College of Philadelphia had also been bargaining for it, and were disappointed over the turn the affair had taken. Mr. Rittenhouse had made a saving clause in his bargain in favor of the College of Philadelphia, in agreement with which he began another orrery for that institution. "This," he said, "I am not sorry for, since the making of the second will be but an amusement compared with the first; and who knows but that the rest of the colonies may catch the contagion? "The sum of two hundred pounds was obtained toward paying for the instrument by means of lectures on astronomy delivered by Rittenhouse's friend, the Rev. Dr. Smith, Provost of the College of Philadelphia, concerning which the Rev. Dr. Peters wrote," The doctor in his introductory lecture was honored with the principal men of all denominations, who swallowed every word he said with the pleasure that attends the eating of the choicest viands,