This 1847 lithograph was used as a plate in a volume about magnetic and meteorological observations; it illustrates an oblique elevation and floor plan of the magnetic observatory building at Girard College in Philadelphia. This was the first magnetic observatory in the United States, constructed on the west grounds of the school in 1839 after designs by architect Thomas Ustick Walter. Labels for instruments are included in the floor plan and include a transit; clock; dew point instrument; telescope declinometer; anemometer and rain gauge; barometer; telescope and horizontal force magnetometer; telescope and vertical force magnetometer; and thermometers. The brainchild of scientist Alexander D. Bache, the observatory was moved to the western ends of the college grounds by master carpenter James O. Sawyer sometime after 1845, and was later used as a carpentry shop. This lithograph was created by artist Rufus S. Mason and was printed by Peter S. Duval, one of the most prominent lithographers and printers of his day.