By Prof. A. E Foote. One of the results of the United States Centennial Exhibition held in Philadelphia, was the establishment of this now celebrated naturalists' agency. Specimens of natural history, in every department, are collected for the use of students ; but perhaps its greatest utility is in the means which it affords scientific men of procuring old and very often essential works, which are no longer issued by their publishers, or, as it is technically called, works out of print. The July number is wholly given up to a catalogue of surgical and medical works. A rough estimate of the books offered gives us 2,260, and we fancy no such complete list of old or scarce medical works has ever been offered before. An enterprise like this deserves universal support. The monthly is sold at seventy-five cents a year, but we suppose specimen copies can always be had by writing for them to Prof. A. E. Foote, Naturalists' Agency, Philadelphia.