These logbooks record two voyages (to Corunna, Spain, 1789-1790, and to Oporto, Portugal, 1791, and returns to Philadelphia), with observations of differences in temperature between air and water, especially when passing the Gulf Stream or any land or banks.

Written by William Alexander at Basking Ridge, New Jersey, March 27, 1773, this essay appeals to the American Philosophical Society to collect and publish astronomical observations. It was sent to the American Philosophical Society, where it was duly read in May 1773.