A few days' practice is not thrown away if the canoist seizes every opportunity of performing under easy circumstances feats which may at other times have to be done under necessity, and which would not be so well done if attempted then for the first time. Let him, therefore, as soon as possible, become adept in crossing above or below a single sunk rock with his _boat's bow pointed to any angle of the semicircle before him_. Next we have to consider the cases in which more than one rock will have to be avoided. Now, however great the number of the rocks may be, they can be divided into sets of three, and in each of the figures 3, 4, 5, 6 it is supposed that (for reasons which may be different in each case, but always sufficient) the canoe has to pass between rocks _A_ and _B_, and then between _B_ and _C_, but must not pass otherwise between _A_ and _C_. In fig. 3 the course is below _B_, and above _C_, being a combination of the instance in fig. 2 with that in fig. 1. The precise angle to the line of the course which the boat's longer axis ought to have will depend upon what is to be done next after passing between _B_ and _C_, and hence the importance of being able to effect the passages in fig. 1 and fig. 2 with the axis at any required angle. We may next suppose that one of the three rocks, say _B_, as in fig. 4, is a breaker which will deflect the current (as indicated by the dotted stream lines), and it will then be necessary to modify the angle of the boat's axis, though the boat's centre has to be kept in the same course as before. It will be seen at once that if _A_ were a breaker the angle would be influenced in another manner, and that if _C_ were a breaker the angle at which the boat should emerge from the group of rocks would be influenced by the stream from _C_ also; but it is only necessary to remind the reader that all the combinations and permutations of breakers and sunk rocks need not be separately discussed,--they may be met by the experience obtained in one case of each class of circumstances.