Letter from William Henry Emory, Washington to Edward Sabine Reference to sending Sabine magnetic observations from the Mexican [boundary survey]. Emory expresses relief to learn the magnetic observations agree with the conjecture lines on Sabine’s provisional map. Emory is preparing a map including some observations made on the new boundary in 1854 to 1855 with a Gambey instrument. Observations on the old line will allow Emory to group the stations advantageously. 30 April 1856