Magnetic Ranges for Compass Deviation San Francisco Bay California.


Cartographer(s): Office of the Coast Survey
Date: 1898
Place: Washington, D.C.
Dimensions: Map: 83 x 61 cm (32.5 x 24 in); Booklet: 14.5 x 23 cm (5.75 x 9 in)
Condition Rating: VG

In stock

SKU: NL-01158 Category: Tags: ,

A late 19th-century San Francisco Bay magnetic variation booklet with views and a map.


A fascinating piece of nautical ephemera, this pamphlet consists of seven pages, with five plates showing ten views plus a folding lithographed map outlining the magnetic ranges navigators should consider while sailing in San Francisco Bay. Lieutenant J.M. Helm, Assistant to the U.S. Navy, chose the ranges.

Navigators need to consider magnetic variations, also known as magnetic declination, because it represents the angle between the magnetic north (the direction the north end of a compass needle points) and the true north (the geographic North Pole). The Earth’s magnetic field is not perfectly aligned with its geographical poles, and this discrepancy can vary depending on the location on Earth.

For navigators, failing to account for magnetic variation can result in significant navigation errors, potentially leading them off course. When plotting a course using a compass, navigators adjust for this variation to ensure their intended path aligns with true directions on a map. Over time and across different geographic locations, magnetic variation changes, which is why updated charts and knowledge about local variations are essential for accurate navigation.


Office of the Coast Survey

The Office of Coast Survey is the official chartmaker of the United States. Set up in 1807, it is one of the U.S. government’s oldest scientific organizations. In 1878 it was given the name of Coast and Geodetic Survey (C&GS). In 1970 it became part of the National Oceanic and Atmospheric Administration (NOAA).

The agency was established in 1807 when President Thomas Jefferson signed the document entitled “An act to provide for surveying the coasts of the United States.” While the bill’s objective was specific—to produce nautical charts—it reflected larger issues of concern to the new nation: national boundaries, commerce, and defense.

Alexander Dallas Bache, great-grandson of Benjamin Franklin, was the second Coast Survey superintendent. Bache was a physicist, scientist, and surveyor who established the first magnetic observatory and served as the first president of the National Academy of Sciences. Under Bache, Coast Survey quickly applied its resources to the Union cause during the Civil War. In addition to setting up additional lithographic presses to produce the thousands of charts required by the Navy and other vessels, Bache made a critical decision to send Coast Survey parties to work with blockading squadrons and armies in the field, producing hundreds of maps and charts.

In 1871, Congress officially expanded the Coast Survey’s responsibilities to include geodetic surveys in the interior of the country, and one of its first major projects in the interior was to survey the 39th Parallel across the entire country. Between 1874 and 1877, the Coast Survey employed the naturalist and author John Muir as a guide and artist during the survey of the 39th Parallel in the Great Basin of Nevada and Utah. To reflect its acquisition of the mission of surveying the U.S. interior and the growing role of geodesy in its operations, the U.S. Coast Survey was renamed the United States Coast and Geodetic Survey (USC&GS) in 1878.

Condition Description

Map in good condition, with some discoloration along fold lines.

Wrappers toned and creased, sticker residue on upper front joint, reference number in red ink in margin, horizontal tear to rear cover with some minor chips.