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' wouldrepresent 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 cxaggerated 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 overestimate.

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

Current

Strong ripples

Island.

Curren

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 stom

achs 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.

CHAPTER VII.

THE GRAND CAÑON OF THE YUKON.

GRAYLING.

WE slowly floated out of Lake Marsh it was known to us by Indian reports that somewhere not far ahead on the course of the river would be found the longest and most formidable rapid on the entire length of the great stream. At these rapids the Indians confidently expected that our raft would go to pieces, and we were therefore extremely anxious to inspect

them. By some form of improper interpretation, or in some other way, we got the idea into our heads that these rapids, rushing," as the natives described them, "through a dark cañon," would be reached very soon, that is, within two or three miles, or four or five at the furthest. Accordingly I had the raft beached at the river's entrance, and undertook, with the doctor, the task of walking on ahead along the river bank to inspect them before making any further forward movement, after which one or both of us might return. After a short distance I continued the journey alone, the doctor returning to start the raft. I hoped to be at the upper

end of the rapids by the time she came in sight so as to signal her in ample time for her to reach the bank from the swiftest current in the center, as the river was now five or six hundred yards wide in places. It turned out afterward that the great rapids were more than fifty miles further on.

I now observed that this new stretch of river much more closely resembled some of the streams in temperate climes than any we had yet encountered. Its flanking hillsides of rolling ground were covered with spruce and pine, here and there breaking into pleasant-looking grassy prairies, while its own picturesque valley was densely wooded with poplar and willows of several varieties. These latter, in fact, encroached so closely upon the water's edge, and in such impenetrable confusion, that camping places were hard to find, unless a friendly spur from the hills, covered with evergreens, under which a little elbow room might be had, wedged its way down to the river, so as to break the continuity of these willowy barriers to a night's good camping place. The raft's corduroy deck of pine poles often served for a rough night's lodging to some of the party.

Muskrats were plentiful in this part of the river, and I could hear them "plumping" into the water from the banks, every minute or two, as I walked along them; and afterward, in the quiet evenings, these animals might at once be traced by the wedge-shaped ripples they made on the surface of the water as they swam around us.

I had not walked more than two or three miles, fighting great swarms of mosquitoes all the way, when I came to a peculiar kind of creek distinctive of this por