REPORT OF THE SECRETARY 19 
The arts and crafts of the American Indian are represented by life- 
size models of Zufi potters, Navaho silversmiths, and Navaho 
blanket weavers at work at their tasks. The work in biology is 
typified by a mounted group of the interesting Bighorn, or Rocky 
Mountain sheep, shown in lifelike poses, which has proved to be a 
most attractive exhibit. Both educational and interesting are the 
geological exhibits, which include a series illustrating how rock is 
weathered to form soil; the gems and precious stones which occur 
in America and the minerals in which they are found; a number 
of interesting fossil forms such as fossil turtles, a giant fossil fish 
which had swallowed another fish, both being preserved in the rock, 
fossil plants from the coal measures of Pennsylvania, and fossil 
algae or seaweed, among the earliest known forms of hfe on the 
earth. 
The vast collection of American historical material in the National 
Museum is represented in the Institution’s Sesquicentennial exhibit 
by a selected series of arms, insignia, uniforms, medals, and decora- 
tions, and by models of Columbus’ ships, of the Mayflower, and 
of the Constitution. Mechanical technology is represented by a very 
complete exhibit showing the development of the steam engine and 
of the steamboat. The progress in photography is illustrated by ex- 
amples of this art from the days of the first daguerreotype to the 
finest modern work, and this graphic arts exhibit also includes ex- 
amples of etching, intaglio engraving, the halftone process, and 
other methods of artistic expression and reproduction. 
The Institution’s work in astrophysics, especially on the study of 
the variation of the sun’s heat, is represented by the instruments 
used in this investigation—the bolometer, an instrument so sensitive 
that it will measure a change in temperature of one-millionth of a 
degree centigrade; the pyrheliometer, which measures the heat 
received on the earth from the sun; and the pyranometer and the 
melikeron, devices which permit the determination of the heat lost 
in passing through the earth’s atmosphere. 
The Smithsonian exhibit contains also a complete set of its publi- 
cations and those of the bureaus under its direction, numbering in 
all nearly 900 volumes, which illustrate one of the Institution’s 
principal means of diffusing knowledge. The entire exhibit was 
brought together and arranged in Philadelphia under the direction 
to Mr. W. de C. Ravenel, administrative assistant to the secretary. 
PUBLICATIONS 
The 11 series of publications issued under the direction of the 
Institution form its chief means of accomplishing “the diffusion 
of knowledge among men,” one of its primary functions. These 
