13 x 16 1/4 in. (image) 14 1/2 x 17 7/8 in. (sheet) albumen photograph mounted on cardstock. Signed "A. Sonrel" lower left.

Louis Agassiz (1807-1873) is featured seated at a table across from Carlile Patterson. Standing between them is Benjamin Peirce, unfurling a scroll, which is featured as a separate albumen photograph cut to shape and affixed to the portrait, upon which is written: "Instructions for Expediti[on]...From Captain C.P. Patterson / Yours respectf- Benjamin Peirce, Superintendent / To Profr. L Agassiz."

This portrait was made during preparations for the US Coast Survey's "Hassler Expedition." The 1871-1872 expedition would take Agassiz and others from the Boston Navy Yard to San Francisco, journeying around Cape Horn, allowing them the ability to explore numerous coastal environments including the Straits of Magellan and the Galapagos Islands. Notably, Agassiz found evidence of glacial activity in the Southern Hemisphere, which was one of his specific goals for the expedition.

Mathematician and astronomer Benjamin Peirce (1809-1880) served as Superintendent of the US Coast Survey from 1867-1874, and Carlile Patterson (1816-1881) was appointed hydrographic inspector of the Survey in 1861, succeeding Peirce as Superintendent in 1874.