ng similar lines, although they came late in
the war, under the leadership of an Australian geologist. Their efforts
were especially useful in connection with the large amount of tunnelling
and mining done on the British front. Among the many unexpected and
special uses of geology might be cited the microscopical identification
of raw materials used in the German cement. It became necessary for
certain purposes to know where these came from. The microscope disclosed
a certain volcanic rock known to be found in only one locality. In the
Palestine campaign, the knowledge of sources of road material and water
supply based on geologic data was an important element in the advance
over this arid region. Wells were drilled and water pipes laid in
accordance with prearranged plans.

In spite of the fact that the usefulness of geology had been clearly
indicated by the experience of the German and British armies, the
American Expeditionary Force was slow to avail itself in large measure
of this tool; but after some delay a geologic service was started on
somewhat similar lines under the efficient leadership of
Lieutenant-Colonel Alfred H. Brooks, Director of the Division of Alaskan
Resources in the U. S. Geological Survey. The work was organized in
September, 1917, and during the succeeding ten months included only two
officers and one clerk. For the last two months preceding the armistice
there was an average of four geologic officers on the General Staff, in
addition to geologists attached to engineering units engaged in road
building and cement making, and plans had been approved for a
considerable enlargement of the geologic force. The work was devoted to
the collection and presentation of geologic data relating to (1) field
works; (2) water supply; and (3) road material. Of these the first two
received the most attention. Maps were prepared, based somewhat on the
German model, for the French defenses of the Vosges and Lorraine
sectors, and for the German defenses of the St. Mihiel, Pont-a-Mousson,
and Vosges sectors. Water supply reports covered nearly 15,000 square
kilometers. The following description of the formations, taken from the
legend of one of the geologic maps, shows the nature of the data
collected:

_Silt, clay and mud, with some limestone gravel_, usually more
or less saturated, except during dry season (June to
September), in many places subject to flooding. Surface
usually soft except du