data, that is, the visiting and examination of a great number of rock exposures well distributed over the area, and the careful location of each upon his topographical map, with observations indicated by special characters and colors. Where the region is thinly settled and roads are few, access will be difficult and the location of exposures doubly so, since no well determined points upon the map will generally be found near at hand from which to fix direction or to measure distance. In the comparatively thickly populated Atlantic section of the United States there will, however, be found large areas within which the highways form an elaborate network, and the location of outcrops will here be comparatively easy; a road corner, a sharp bend of a highway, a house, or other characteristic landmark being generally near enough to furnish a basis of measurement. It is for a study of such areas that the present paper is especially intended.
In the past the field geologist engaged in areal and structural work has depended either upon his own power of locomotion or upon the use of a saddle horse or a team. In the northeastern United States the numerous fences restrict his use of a horse to the highways themselves, and the difficulty of hiring suitable saddle horses has practically eliminated them from consideration. When teams are used they must very frequently be left while rock exposures are sought or examined, and the time thus lost in hitching in suitable places is very considerable. Further, a horse requires food and water, protection from flies, etc., and its hire varies from one to three dollars per day.
The advent of the bicycle has greatly facilitated the study of regions where roads are frequent, though geologists seem to be slow to appreciate its advantages. The increasing number of official government or State geologists, of university professors, and of teachers and students generally who engage in geological work may well excuse one for urging the advantages in effectiveness, in cheapness and in comfort of a properly equipped bicycle for this and similar forms of scientific work. One of the greatest of these advantages arises from the attached cyclometer, which if read and recorded at road corners and other landmarks affords one at all times either a perfect location (in case an exposure is found on the highway), or a convenient base (if an excursion must be made away from the road).
The most convenient form of cyclometer for geological work is one which can be attached to the axle of the forward wheel of the bicycle between the prongs of the fork. The slight disadvantage of being compelled to bring the wheel to a definite position before reading the cyclometer is small when compared to the danger of injuring the usual form through the falling of the wheel or from contact with objects by which the wheel is left supported. It is, moreover, frequently desirable to ship the wheel as baggage on railway trains, and it is generally better on
