With mimic orbs the labors of the skies."
This was Barlow's way of telling of the achievement of David Rittenhouse, the colonial astronomer, in fashioning the marvellous orrery, the mechanical representation of the movements of the planetary system. Thomas Jefferson's prose description was a little more readable:
"A machine far surpassing in ingenuity of contrivance, accuracy and utility anything of the kind ever before constructed.... He has not indeed made a world, but he has by imitation approached more its Maker than any man who has lived from the creation to this day."
The father of the maker of the orrery was a paper manufacturer near Germantown, but when David was three years old he moved to a little farm in Norriton, nineteen miles from Philadelphia, where, in 1749, he built the stone house in which his son spent the rest of his life.
It was his purpose to make a farmer of David, and he might have succeeded if he had not invested in a few mathematical books. The twelve-year-old boy was fascinated by these volumes. Samuel W. Pennypacker has told the result:
"The handles of his plough, and even the fences around the fields, he covered with mathematical calculations.... At seventeen he made a wooden clock, and afterward one in metal. Having thus tested his ability in an art in which he had never received any instruction, he secured from his somewhat reluctant father money enough to buy in Philadelphia the necessary tools, and after holding a shop by the roadside, set up in business as a clock and mathematical instrument maker."
Dr. Benjamin Rush once said that "without library, friends, or society, and with but two or three books, he became, before he had reached his four-and-twentieth year, the rival of two of the greatest mathematicians of Europe."
The skilled astronomer was soon called upon to render a service to several of the Colonies. By means of astronomical instruments he did such accurate work in marking out the boundary between Delaware and Pennsylvania that Mason and Dixon later accepted his results, and he settled the dispute between New Jersey and New York as to the point where the forty-first degree of latitude touches the Hudson River. Perhaps, however, the achievement that won for him greatest fame was the observation, made in 1769, of the transit of Venus. The importance of the observation is evident from the facts that it provides the best means for calculating the distance between the heavenly bodies, which had never been satisfactorily made, and that the opportunity would not occur again for one hundred and five years. After months of preparation, which included the making of delicate instruments, Rittenhouse, one of a committee of three appointed by the American Philosophical Society, succeeded. In the words of Pennypacker, "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."
Benjamin Franklin found in him a kindred spirit, and the Philadelphian was frequently a visitor at the Norriton farmhouse. On Sunday the two friends often went to the old Norriton Presbyterian Church, which had been built on the corner of the Rittenhouse farm, within sight of the house. This church, which probably dates from 1698, is still standing in good repair.
Some years after the successful observation of the transit of Venus brought fame to the American astronomer, he moved to Philadelphia. There, among other duties, he had charge of the State House clock.