One of the most prominent scientific refugees from the political turmoil of 1848, Arnold Guyot made fundamental contributions to the study of geology, glaciology, and meteorology on two continents. After emigrating to the United States, Guyot established himself as Professor of Geology and Physical Geography at Princeton, remaining untilhis death in 1884. The Guyot Collection consists of 61 letters written by Louis Agassiz (15 items), his wife Elizabeth (32), and their son Alexander (14), to their friend and fellow naturalist, Arnold Guyot. Primarily personal in nature, the letters reflect a long and intimate friendship, making frequent mention of family and mutual friends. There is, however, comparatively little in the collection relating to their respective scientific endeavors, with only a few references to the situation at the Museum of Comparative Zoology and at Princeton, to publications of various sorts, to the difficulties of their mutual friend Leo Lesquereux, and to other colleagues.

Leo Lesquereux emigrated from his native Switzerland to Ohio in 1848, and quickly established himself as one of America's foremost bryologists and paleobotanists. Working with the state geological surveys of Pennsylvania and several states in the Mississippi Valley, he contributed some of the earliest descriptions of the Carboniferous flora in North America and helped flesh out the basic geology of coal formation. The autobiography of Leo Lesquereux provides an engaging account of the early life of one of Victorian America's best known bryologists and paleobotanists. Consisting of 14 letters addressed to his friend, J. Peter Lesley, the letters cover only the years between Lesquereux's childhood in Switzerland and his emigration to the United States in 1848. Written after his retirement at the age of 78, they shed light on his education, the illness that led to his loss of hearing, and his studies of peat deposits in Europe, and they provide short vignettes about watchmaking and about his peers Louis and August Agassiz and Arnold Guyot.

This correspondence concerning the survey of western lands was received by the United States Geographical and Geological Survey of the Rocky Mountain Region. Also includes a selection of letters sent by the Survey (1876-1878).

These are letters to Quetelet primarily on the subject of astronomy (meteorological observations), including charts showing directions of shooting stars.