When he observed the contact, and the planet had fairly entered the sun’s disk, his emotions so overpowered him that he sank fainting to the ground, unable to bear the intense feelings of delight which attended the consummation of the long hoped for event. Rising from his exhaustion, he proceeded to measure the distance between the centers of the two bodies at stated intervals during the transit.
The observations of Rittenhouse were received with interest by scientific men everywhere. Subsequently they were found to be nearly accurate and his computations placed him among the greatest of astronomers. The royal astronomer of England bore testimony to their value and another high authority said:
“The first approximately accurate results in the measurements of the spheres were given to the world, not by 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.”
On November 9 of the same year David Rittenhouse made an observation of the transit of Mercury, which was the fourth ever witnessed. About this time he also determined the difference of the meridians of Norriton and Philadelphia.
David Rittenhouse was without doubt the first inventor of a practical planetarium, erroneously called the “orrery,” an instrument so constructed as to exhibit the movements of the planets around the sun. In theory the idea was not new. Such an instrument had been made for the Earl of Orrery in 1715, but this was a mere toy and gave the movements of only two heavenly bodies.
Rittenhouse determined that he would make an elaborate instrument, based on scientific principles and on the astronomical calculations which he had prepared. After three years of labor, in 1779, the “Rittenhouse orrery” was completed.
This orrery was purchased by Princeton University for £300. The trustees of the College of Philadelphia were offended, but Rittenhouse immediately set to work and constructed a duplicate, which was purchased for the college by the proceeds of a series of lectures on astronomy by Dr. William Smith, provost of the college.
The second orrery was much larger than the original, but was constructed on the same model. This was sold for £400.
David Rittenhouse was elected one of the secretaries of the American Philosophical Society in 1771. He delivered a most elaborate address before the society February 23, 1775, entitled “An Oration on Astronomy.” This address was inscribed and dedicated to the delegates assembled in the Continental Congress. In 1790 he became one of its vice presidents.
On the death of Dr. Franklin he succeeded to the office of president, January, 1791, which office he held until his death, when he was succeeded by Thomas Jefferson.