Looking back, it seems almost miraculous that a raft could make a voyage of over thirteen hundred miles, the most difficult part of which was unknown, starting at the very head where the stream was so narrow that the raft would have been brought at a standstill if it swung out of a straight course end on (as it did in the Payer Rapids), and covering nearly two months of daily encounters with snags and bowlders, sticking on bars and shooting rapids, and yet get through almost unscathed. When I started to build this one on Lake Lindeman I had anticipated constructing two or three of these primitive craft before I could exchange to good and sufficient native or civilized transportation.
The raft is undoubtedly the oldest form of navigation extant, and undoubtedly the worst; it is interesting to know just how useful the raft can be as an auxiliary to geographical exploration, and certainly my raft journey was long enough to test it in this respect.
The raft, of course, can move in one direction only, viz.: with the current, and therefore its use must be restricted to streams whose upper waters can be reached by the explorer. The traveler must be able to escape by the mouth of the stream or by some divergent trail lower down, unless his explorations prove the river to be navigable for such craft as he finds on its lower waters, when he may use these for returning. The building of a raft requires the presence of good, fair-sized timber along the stream. The river too, must offer no falls of any great size. My journey, however, has demonstrated that a well constructed raft can go any where, subject to the above restrictions, that a boat can, at least such a boat as is usually employed by explorers.
I know of nothing that can give an explorer a better opportunity to delineate the topography of the surrounding country with such instruments as are commonly used in assisting dead reckoning, than is afforded by floating down a river. I believe the steady movement with the current makes "dead reckoning" much more exact than with a boat, where the rate of progress is variable, where one hour is spent in drifting as a raft, another in rowing, and a third in sailing with a changeable wind, and where each mode of progress is so abruptly exchanged for another. Any steady pace, such as the walking of a man or a horse, or the floating of a raft carefully kept in the axis of the current, makes dead reckoning so exact, if long practiced, as often to astonish the surveyor himself, but every thing depends upon this steadiness of motion. The errors in dead reckoning of Mr. Homan, my topographer, in running from Pyramid Harbor in Chilkat Inlet to Fort Yukon, both carefully determined by astronomical observations and over a thousand miles apart, was less than one per cent., a fact which proves that rafting as a means of surveying may be ranked with any method that requires walking or riding, and far exceeds any method in use by explorers ascending a stream, as witness any map of the Yukon River that attempts to show the position of Fort Yukon, before it was astronomically determined by Captain Raymond. Meridian observations of the sun for latitude are hard to obtain, for the reader already knows what a task it is to get a raft into camp. This difficulty of course will vary with the size of the raft, for one as large as ours would not always be needed and a small one can be more readily handled in exploration. While rafting, field photography, now so much used by explorers, is very difficult, as it can only be achieved at camping places unless the apparatus is carried ashore in a canoe, if the raftsmen have one; and the ease with which separated persons can lose each other along a river full of islands makes this kind of work a little uncertain, and the services of a good artist more valuable.
This summary covers nearly all the main points that are strictly connected with geographical exploration, in the meaning ordinarily accepted; but on expeditions where this exploration is the main object there are often other matters of a scientific nature to be taken into account, such as the geology, botany, and zoölogy of the districts traversed, to which the question of geographical distribution is important, and for all these objects researches by means of a raft are at considerable disadvantage.
Also in rafting there is a slight tendency to over-estimate the length of the stream, although the map may be perfectly accurate. In the figure on page [152], the axis AA' is undoubtedly the accepted line on which to estimate and measure the length of the stream between those two points, and it is equally evident to one familiar with the currents of a river that some such line as RR' would represent the course of a floating raft, and the excess of RR' over AA', both being developed, would be the error mentioned. In this figure the relative curves are exaggerated to show the principle more clearly. Again, every island and shoal would materially affect this somewhat mathematical plan, but I think even these would tend to produce an over-estimate.
Drifting close along the shores of an island, and nearing its lower termination, we occasionally were delayed in a singular manner, unless prompt to avoid it. A long, narrow island, with tapering ends, and lying directly in the course of the current, gave us no trouble; but oftentimes these lower ends were very blunt, and the currents at the two sides came at all angles with respect to the island and each other, and this was especially true of large groupings of islands situated in abrupt bends of the river. To take about the worst case of this nature that we met, imagine a blunted island with the current at either side coming in at an angle of about forty-five degrees to the shore line, or at right angles to each other, as I have tried to show in figure on this page, the arrows showing the current. At some point below the island the recurving and ex-curving waters neutralize each other in a huge whirlpool (W). Between W and the island the waters, if swift, would pour back in strong, dancing waves like tide-rips, and in some places with such force as to cut a channel (C) into the island. It is evident that with the raft at R, it is necessary to row to starboard as far as R' before W is reached, as otherwise it would be carried back against the island. We got caught in one violent whirlpool that turned the huge raft around so rapidly that I believe the tender stomachs of those prone to sea-sickness would soon have weakened if we had not escaped by vigorous efforts. At great angles of the swift water and broad-based islands I have seen the whirlpool when nearly half a mile from the island, and they were usually visible for three or four hundred yards if worth noticing. So many conditions were required for the creation of these obstacles that they were not common.