His letters show how constantly during this nominal vacation his Museum and its interests occupied his thoughts. One is to his brother-in-law, Thomas G. Cary, whose residence was in San Francisco, and who had been for years his most efficient aid in obtaining collections from the Pacific Coast. TO MR. THOMAS G. CARY. CAMBRIDGE, March 23, 1863. DEAR TOM, For many years past your aid in fostering the plans of the Museum in Cambridge has greatly facilitated the progress of that establishment in everything relating to the Natural History of California, and now that it has become desirable to extend our scheme to objects which have thus far been neglected I make another appeal to you. Every day the history of mankind is brought into more and more intimate connection with the natural history of the animal creation, and it is now indispensable that we should organize an extensive collection to illustrate the natural history of the uncivilized races. Your personal acquaintance with business friends in almost every part of the globe has suggested to me the propriety of addressing to you a circular letter, setting forth the objects wanted, and requesting of you the favor to communicate it as widely as possible among your friends. To make the most instructive collections relative to the natural history of mankind, two classes of specimens should be brought together, one concerning the habits and pursuits of the races, the other concerning the physical constitution of the races themselves. With reference to the first it would be desirable to collect articles of clothing and ornaments of all the races of men, their implements, tools, weapons, and such models or drawings of their dwellings as may give an idea of their construction; small canoes and oars as models of their vessels, or indications of their progress in navigation; in one word, everything that relates to their avocations, their pursuits, their habits, their mode of worship, and whatever may indicate the dawn or progress of the arts among them. As to articles of clothing, it would be preferable to select such specimens as have actually been worn or even cast off, rather than new things which may be more or less fanciful and not indicate the real natural condition and habits of a race. With regard to the collections intended to illustrate the physical constitution of the races it is more difficult to obtain instructive specimens, as the savage races are generally inclined to hold sacred all that relates to their dead; yet whenever an opportunity is afforded to obtain skulls of the natives of different parts of the world, it should be industriously improved, and good care taken to mark the skulls in such a way that their origin cannot be mistaken. Beside this, every possible effort should be made to obtain perfect heads, preserved in alcohol, so that all their features may be studied minutely and compared. Where this cannot be done portraits or photographs may be substituted.