These two kinds of engravings may, for the sake of convenience, be distinguished as “deep” and “shallow,” respectively, according as the figures are deeply cut into the rock or are merely scratched on the surface. The former vary from one-eighth to one-half of an inch, or even more, in depth; the latter are of quite inconsiderable depth. This difference probably corresponds with a difference in the means by which they were produced. The deep engravings seem cut into the rock with an edged tool, probably of stone; the shallow figures were apparently formed by long continued friction with stones and moist sand. The two kinds seem never to occur in the same place or even near to each other; in fact, a distinct line may almost be drawn between the districts in which the deep and shallow kinds occur, respectively; the deep form occurs at several spots on the Mazeruni, Essequibo, Ireng, Cotinga, Potaro, and Berbice rivers. The shallow form has as yet only been reported from the Corentyn river and its tributaries, where, however, examples occur in considerable abundance. But the two kinds differ not only in the depth of incision, in the apparent mode of their production, and in the place of their occurrence, but also--and this is the chief difference between the two--in the figures represented. Fig. 106 is a typical example of the shallow carvings. [Illustration: FIG. 106.--Shallow carvings in Guiana.] Fig. 1104, infra, is a similar example of the deep carvings. The shallow engravings seem always to occur on comparatively large and more or less smooth surfaces of rock, and rarely, if ever, as the deep figures, on detached blocks of rock, piled one on the other. The shallow figures, too, are generally much larger, always combinations of straight or curved lines in figures much more elaborate than those in the deep engravings; and these shallow pictures always represent not animals, but greater or less variations of the figure which has been described. Lastly, though I am not certain that much significance can be attributed to this, all the examples that I have seen face more or less accurately eastward. The deep engravings, on the other hand, consist not of a single figure but of a greater or less number of rude drawings. * * * These depict the human form, monkeys, snakes, and other animals, and also very simple combinations of two or three straight or curved lines in a pattern, and occasionally more elaborate combinations. The individual figures are small, averaging from 12 to 18 inches in height, but a considerable number are generally represented in a group. Some of the best examples of this latter kind are at Warrapoota cataracts, about six days’ journey up the Essequibo.