SKETCH OF DAVID RITTENHOUSE. 837 



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 computa- 

 tions, which was that " the force wherewith a man acts when he 

 lifts a weight of two hundred pounds, if applied without inter- 

 mission 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, con- 

 tinue 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 con- 

 spicuous, 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 igno- 

 rant in astronomy a just view of the solar system; but would 

 rather astonish the skillful and curious examiner by a most accu- 

 rate 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 astro- 

 nomical 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 Prince- 

 ton 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 Rit- 

 tenhouse'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, 



