Treat sent this volume to Thomas Jefferson in 1809 from "Arkansa in Louisiana," and wrote, "If from their perusal you can derive, either information or amusement, respecting the climate of this part of our country, your acceptance will be highly gratifying."

This journal was kept on a voyage from the Downs to the Capes of Delaware on board the ship Three Sisters, 26 June-20 August, 1803. The volume includes "Observations on the storm glass," made on the same voyage. The storm glass, with an explanation of its use, and the journal of observations are at the American Philosophical Society.

The first volume contains notes of expenses and of observations while surveying the western boundary of Pennsylvania (1785). Mentions APS under date of Feb. 20, 1784. The second volume contains observations that were continued after Rittenhouse's death to Sept. 30, 1805.

This volume contains medical notes by Wistar, including observations on yellow fever and arguments to prove its foreign origin, facts relative to the progress of the fever in 1797, the infection and death of Colonel Van Emburgh, the infection of the crew of the ship "Deborah" and of the Durham boat (1802), an account of the diseases which afflicted the family of James Hammar in Montgomery County (Pa.), facts relating to the typhus fever of 1812-1813, case histories (1796-1803), temperature chart (1758-1759, 1760), and a thermometrical journal (1760-1765) kept by Charles Norris and copied by Wistar from notes in possession of Joseph Parker Norris.