=The Ethnological Heads.=--The ethnological heads ornamenting the keystones of the first-story pavilion windows offer as interesting material for study as any of the decorations of the Library. The series is unique in that it is the first instance of a comprehensive attempt to make ethnological science contribute to the architectural decoration of an important public building. It was at first proposed to employ a more conventional kind of ornament, such as the familiar Gorgons’ heads so often found in connection with Renaissance architecture. The present idea was carried out with the assistance of Professor Otis T. Mason, the Curator of the Department of Ethnology in the National Museum for the last twelve years. The heads, thirty-three in number, are about a foot and a half in height, and were modelled, some by Mr. Boyd and others by Mr. Henry J. Ellicott, after data accumulated by Professor Mason as the result of some six months’ special study of the ethnological collections in the possession of the National Museum--which contains, indeed, practically all the material (books, photographs, carefully verified measurements) necessary for such an undertaking. The large collection of authentic, life-size models, chiefly of savage and barbarous peoples, which the visitor may see in its exhibition halls, is the most extensive in the country, and many of the heads on the Library keystones are taken directly from these. [Illustration: ARAB. TURK. MODERN EGYPTIAN.] Taking into consideration the difficulty of obtaining the more delicate differentiation of the features in a medium so unsatisfactory, from its coarseness of texture, as granite, the result of Professor Mason’s work is one of the most scientifically accurate series of racial models ever made. Still another difficulty, it may be added, lay in the fact that each head had to be made to fit the keystone. Besides the necessity of uniform size, the architect demanded also, as far as possible, a generally uniform shape, which it was often very hard to give and still preserve the correct proportions of the racial type. The face had to be more or less in line with the block it ornamented, and, especially, the top of the head had to follow, at least roughly, a certain specified curve. This last point was met either by using or not using a head-dress, whichever best met the difficulty. In one case the problem was a little puzzling--that of the Plains Indian, with his upright circlet of eagle’s feathers, which were bound to exceed the line, if accurately copied. The difficulty was frankly met by laying the feathers down nearly flat upon the head. [Illustration: ABYSSINIAN. MALAY. POLYNESIAN.]