Under such circumstances as these, the familiar intercourse between David Rittenhouse and his young friend Barton, which commenced when the age of the former did not exceed nineteen years, could not fail to prove highly advantageous to the mental improvement of both. The one possessed a sublime native genius; which, however, was yet but very imperfectly cultivated, for want of the indispensable means of extending the bounds of natural knowledge: the other had enjoyed the use of those means, in an eminent degree, and thus justly acquired the reputation of a man of learning. A reciprocation of these different advantages, as may be well supposed, greatly promoted the intellectual improvement of both. It will be readily conceived, that Mr. Barton’s knowledge of books must have rendered even his conversation instructive to Mr. Rittenhouse, at so early a period of his life. But the former so greatly admired the natural powers of his young friend’s mind, that he took a delight in obtaining for him access to such philosophical works, and other useful books, as he was then enabled to procure for his use; besides directing, as far as he was capable, the course of his studies. After Mr. Barton’s removal to Philadelphia and while he resided in that city, his means of furnishing his friend with books, suitable for his instruction, were greatly enlarged; an advantage of which he most assiduously availed himself: and it is supposed to have been about this time, that a small circulating library was established in Norriton, at the instance of Mr. Barton, zealously seconded by the co-operation and influence of Mr. Rittenhouse. Finally, when Mr. Barton returned from England, in the year 1755—at which time Mr. Rittenhouse was yet but twenty-three years of age, he brought with him a valuable addition to his friend’s little library; consisting, in part, of books which he himself had commissioned Mr. Barton to purchase for him.[74] ----- Footnote 74: The zeal and attention with which our young philosopher pursued his early studies, and such mechanical objects as are more intimately connected with those branches of natural philosophy to which he was most devoted, will appear from the following extract of a letter, addressed by him to Mr. Barton, on the 20th of September, 1756, being then little more than twenty-four years of age; viz. “I have not health for a soldier,” (the country was then engaged in war,) “and as I have no expectation of serving my country in that way, I am spending my time in the old trifling manner, and am so taken with optics, that I do not know whether, if the enemy should invade this part of the country, as Archimedes was slain while making geometrical figures on the sand, so I should die making a telescope.” -----