Popular Science Monthly/Volume 58/March 1901/The Geologist Awheel

From Wikisource
Jump to navigation Jump to search

THE GEOLOGIST AWHEEL.
By Professor WILLIAM H. HOBBS,

UNIVERSITY OF WISCONSIN.

IN no country of the world does the government distribute to its people with so lavish a hand as in our own the published results of scientific investigation. One example among many that might be given is furnished by the reports of the United States Geological Survey, which for abundance of material, for scientific value and for beauty of illustration are not approached by the geological publications of any European state. Of the many who see the beautifully colored geological maps which accompany these magnificent reports, or the only less elaborate and expensive maps prepared by certain of the individual States, doubtless few have the faintest notion of the studies on which they are based.

No comprehensive study can be made of the geology of any region until some sort of geographical map of the region makes it possible to represent the exposed rock masses in approximately their true positions relative to one another. If the geology be other than of the very simplest character—and this will generally be true of mountainous regions—it is not only necessary to fix the geographical positions of rock masses, but their elevations as well. In other words, the map must not only be a plan, but special elevations must be represented, known as geological sections. The most satisfactory representation—and this will be essential for all difficult areas—will be one which shows not only special elevations, but the topographic relief of every point in the area. A proper preparation for detailed geological work in a difficult area involves, therefore, the making of a relief or topographic map based on correct triangulation, and of a scale and an accuracy of delineation of relief forms commensurate with the complexity of the geological structure. For large areas of the eastern United States such maps have been prepared by the United States Government, sometimes in cooperation with the State governments, and these maps maybe obtained in the form of beautifully engraved atlas sheets by any one and at merely nominal prices. On these maps are shown in black the railroads, highways, houses, etc. (the culture); in blue, the lakes, streams, swampy areas, etc. (the hydrography); and in brown, the lines of approximately equal altitude (the topography).

With such a map the field geologist can begin intelligently his geological work. This work will consist first of all in the collecting of his 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 these occasions to remove the ordinary type of cyclometer lest it be broken or injured in handling. All this danger is avoided in the improved form of cyclometer which is attached to the center of the axle.

The equipment of the geologist will generally consist of a collecting bag with separate compartments for note book, maps, and rock specimens; a hammer, compass and aneroid barometer. In regions of low relief the aneroid is of little service and may be dispensed with, but the best method of carrying the other articles of the geologist's equipment is a question of considerable importance.

The collecting bag which is in use by government parties operating in the northern Atlantic States may be deserving of a special description, inasmuch as it is an evolution of many years. It is made of the best grade of russet leather and has four compartments. The map compartment is merely a double back within which the maps, properly protected, are slipped. The note book compartment is sewed on the front of the bag and shaped to the book. In the main central compartment of the bag the specimens are stowed and in a wide but shallow pocket sewed to its back near the top are kept the black and colored pencils, the eraser, horn protractor, and small ebonite triangle, for use in the making of notes and in plotting the observations upon the map. The cover of the bag is a flap fastened by a strap to a buckle on the front and near the bottom of the note book compartment. When carried on the person the bag is supported by a wide strap passing through loops on the sides and bottom so as to carry the weight from below. On the wheel the bag is supported by a light framework of strong galvanized iron wire, which by means of three leather straps is securely fastened to the handle bar and the head of the machine. The bag fits loosely into the frame, even when filled with specimens, and it is kept in place on rough roads by being attached by two straps furnished with snaps to the handle bar of the bicycle. The bag can thus be almost instantly attached to the wheel or removed from it and slung by the carrying strap over the shoulder.

The topographic map sheets which are used for the base in the geological work are cut in half and each of these halves is again divided so as to be mounted on the inside of two cloth covered and hinged boards, as is the lining to a book cover. This method of mounting secures a smooth surface and a firm support to the map, gives a large area always at hand so that geological relationships may be easily appreciated, and furnishes moreover the best possible protection to the records of the work. Hardly less important is the protection which these stiff boards afford to the leather back of the bag when they are slipped within its map compartment, and also to the body of the geologist when the bag is loaded with heavy specimens and carried from the shoulder.

The best form of compass is doubtless the four-inch aluminum dial compass with clinometer attachment, which is manufactured by Gurley for the United States Geological Survey, but cheaper and simpler instruments can be made to serve almost as well. This instrument is best carried in a leather box worn upon the belt. The aneroid, if used, is carried in a leather case slung from the shoulder and passed under the belt so as to be shaken as little as possible. The hammer is most conveniently carried upon the person by slipping the handle through the belt, a 'pick' or prospector's form being specially secure in this position because of its long head. When riding the hammer is slipped under a strap on the side of the carrying frame of the rock bag.

Where observations must be frequently taken, as in detailed areal mapping, considerable time may be lost in finding a suitable support against which to rest the wheel. Bicycle manufacturers should be able to devise a light and simple support which can be carried with the wheel and quickly adjusted. In a region adapted to bicycle work, such as much of the Piedmont Plateau and the Coastal Plain of the eastern United States, as well as large areas in Europe, it is believed that a bicycle outfit such as is here described makes it possible to reduce greatly the expense and to divide by at least one-half the time necessary for mapping over that required if older methods of locomotion and transportation are employed. The inertia of long-established practise is, however, considerable, and geologists have been somewhat slow to adopt the newer methods. The small expense of such an equipment and the accessibility of the beautiful government maps make it possible for private and essentially amateur geologists, with the advantages of only a brief geological training and a moderate amount of experience, to collect valuable data within the area surrounding their homes, especially if these chance to be in a thickly settled part of the country.