. Bulletin. Ethnology. L-poiNT OF Stone and Sec- tion OF BORING. point used is indicated by the form of the perforation. The frequency with which objects are found bored from both sides is proof that the Indian appreciated the ad- vantage of reducing friction. Progress in the elaboration of drills consisted mainly in heightening speed of revolution. If the drill-point be of wood much depends on its hard- ness, for when too h a r d the w o o d grinds the sand to powder, while if it be too soft the grains catch at the base of the cavity and cut away the shaft. Only wood of proper texture holds t
. Bulletin. Ethnology. L-poiNT OF Stone and Sec- tion OF BORING. point used is indicated by the form of the perforation. The frequency with which objects are found bored from both sides is proof that the Indian appreciated the ad- vantage of reducing friction. Progress in the elaboration of drills consisted mainly in heightening speed of revolution. If the drill-point be of wood much depends on its hard- ness, for when too h a r d the w o o d grinds the sand to powder, while if it be too soft the grains catch at the base of the cavity and cut away the shaft. Only wood of proper texture holds the sand as in a matrix and enables it to cut to the best advantage. The insides of drill holes show by the character of their striae whether the cut- ting was accomplished by direct pressure or with the aid of sand. The simplest form of drill was a straight shaft, varying from a fourth to three- fourths of an inch in diameter and from 10 in. to 2 ft in length. This shaft was revolved in alternating directions between the hands, or, when the shaft was held horizontally, it was rolled up and down the thigh with the right harid, the point of the drill being pressed against the object held in the left hand; or at times the object was held between the naked feet while the drill was revolved between the hands. This drill was in use at the time of Coluu)bus and is the only one represented in the Mexican codices (Kings- borough, An- tiq. of Mex., I, pi. 39). With the exception of the strap drill, which was apparently used only in the far N., this is the only form of drill referred to by early Amer- ican writers. The strap drill, used both as a fire drill and as a perforator, is an improvement on the shaft drill, both in the number of its revolutions and in the pressure which may be imparted to the shaft. The shaft is kept in position by means of the head- Seotion of Bead BICONICAL PERFORA. Please note that these images are extracted from scanned page images that may have been digitally
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