The reformation of the Julian calendar by pope Gregory XIII, in the year 1582, is so near the truth, that it will not want correction until 3600 years after the change of stile took place. It has been found by a series of observations noticed in Vince’s astronomy, that the tropical year is 365 days, 5 hours, 48 minutes, 48 seconds; if this be multiplied by 3600 years, the product will be 1,314,872 days, without the fraction of a second. In this period of 3600 years there will be 873 leap years and 2727 common years, which would make one day or 24 hours more than the product above mentioned; it will be necessary therefore, that the 3600th or some intermediate year, reckoned as Bissextile, should be made a common year; or in other words, that there must be 872 leap years and 2728 common years; for if we multiply 872 by 366 days, and 2728 by 365, the sum of the products will be 1,314,872 days, agreeing exactly with 3600 tropical years, according to the most accurate observations hitherto made. I wish to turn your attention and that of the American Philosophical Society to this subject, for altho’ the time is so far distant as not to affect many generations to come, yet I should be glad that the correction should be proposed in the United States of America, rather than in Europe, or any other part of the world.