Page:Popular Science Monthly Volume 58.djvu/525

Rh 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