The study should provide for each rock or its characteristic variety a constant, precisely defined figure, expressing its relationship to percussive hole drilling method adopted in this case. The most desirable it would be to obtain figures that, while depending entirely on the petrographic nature of the rocks being studied, would, on the other hand, be completely independent of factors such as the force of the drill impact, the diameter of the drill, its point angle, the angle of rotation of the drill, etc. In the case when it is impossible to exclude the influence of all these factors, the study should provide figures that depend only on some of them, in which case, all the studied rocks must be compared in exactly the same conditions. Figures of the first kind could then be called absolute, and of the second - only relative.