Nor is it out of place to inquire thus at length into this matter, for I can assure you that one or two blunt slaps on the head from these ropes across a river make it at least interesting if not pleasant to examine "the reason why." And now we have got the philosophy of the thing, let us leave the ropes behind. The actual number of miles in a day's work is much influenced by the number of waterfalls or artificial barriers which are too dry or too high to allow the canoe to float over them. [Illustration: "Shirking a Fall."] In all such cases, of course, I had to get out and to drag the boat round by the fields, as has been already described (p. 80); or to lower her carefully among the rocks, as is shown in the accompanying sketch, which represents the usual appearance of this part of the day's proceedings. Although this sort of work was a change of posture, and brought into play new muscular action, yet the strain sometimes put on the limbs by the weight of the boat, and the great caution required where there was only slippery footing, made these barriers to be regarded on the whole as bores. Full soon however we were to forget such trifling troubles, for more serious work impended. The river banks suddenly assumed a new character. They were steep and high, and their height increased as we advanced between the two upright walls of stratified gravel and boulders. A full body of water ran here, the current being of only ordinary force at its edges, where it was interrupted by rocks, stones, and shingle, and was thus twisted into eddies innumerable. To avoid these entanglements at the sides, it seemed best, on the whole, to keep the boat in mid-channel, though the breakers were far more dangerous there, in the full force of the stream. I began to think that this must be the "hard place coming," which a wise man farther up the river had warned me was quite too much for so small a boat, unless in flood times, when fewer rocks would be in the way. In reply, I had told him that when we got near such a place I would pull out my boat and drag it along the bank, if requisite. To this he said, "Ah! but the banks are a hundred feet high." So I had mentally resolved (but entirely forgot) to stop in good time and to climb up the rocks and investigate matters ahead before going into an unknown run of broken water. Such plans are very well in theory, but somehow the approach to these rapids was so gradual, and the mind was so much occupied in overcoming the particular difficulty of each moment, that no opportunity occurred for rest or reflection. The dull heavy roar round the corner got louder as the Rob Roy neared the great bend. For here the river makes a turn round the whole of a letter S, in fact very nearly in a complete figure of 8, and in wheeling thus it glides over a sloping ledge of flat rocks, spread obliquely athwart the stream for a hundred feet on either hand, and just a few inches below the surface.