to the connection of those two rivers by a canal; in 1773 he was appointed president of a commission to make the river Schuylkill navigable, a duty which they performed by constructing rough dams, and which was continued for a number of years; and in 1774 he and Samuel Holland, commissioners from their respective provinces, fixed the northeastern extremity of the boundary between New York and Pennsylvania.
In 1770 he prepared for the publications of the American Philosophical Society a paper giving a method of ascertaining the true time of the sun's passing the meridian that attracted the attention of Von Zach, the Saxon astronomer. He was chosen one of the secretaries of that society in 1771, and on the 24th of February, 1775, he read before it an oration upon the subject of astronomy. This oration is the most elaborate of his literary productions. The language is simple, the style strong and clear, and it displays much research and special knowledge. In it he traces the history of astronomical discoveries and progress down to the time at which he wrote, but the most interesting portion of the address, as a test of his own acumen, is that in which he endeavors to forecast the future, and to point out the most promising paths for further investigation. The possibility of the existence of the planets that were then unknown seems to have occurred to him, for he says, “The telescope had discovered all the globes whereof it is composed, at least as far as we yet know.” He believed in the existence of beings differing from man more or less in their natures on the other planets. The spots on the sun he conjectured to be solid and permanent cavities, darkened by matter that occasionally and accidentally collected in them. But it was among the fixed stars that with correct inference he expected the greatest discoveries to be made; and the
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