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.

This volume was made at Wilmington, Delaware, for determining the longitude, from 1 July-14 October. It records the position of selected stars and planets. Contains also: Note regarding his astronomical clock, and entries relative to his work in continuing the Mason & Dixon's line.

This volume contains calculations of the distances of stars, eclipses, and longitude, made by William Maule, James Cresson, Joseph Jeanes, James James, and Robert Hutchinson, pupils in the Friends Academy, where Roberts was a teacher.

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.