information as to how he estimated his distances. In a river flowing through a densely wooded country, with nowhere more than a few hundred yards of clear ground on its banks, with a very crooked and twisted course, and with a current varying from being scarcely perceptible to such rapidity that a whole crew of paddlers can hardly make way against it, it is exceedingly difficult to ascertain the rate of motion in miles per hour.

Canoes of different sizes do not travel at very different rates, when each has its complement of men, and I had taken many opportunities to ascertain this rate in still water. Then, by noting the time occupied for a particular distance, say between two of the cataracts, both during the ascent and descent of the river, the mean of the two would be the time if there were no current. Making a little allowance for the load in the canoe, the number or the quality of the rowers, etc., this time multiplied by the rate of travel in still water would give the distance. This was the plan I adopted in making my map of the Uaupés. It is, of course, a mere approximation, and liable to considerable errors, but I did not think they would lead to such a large difference of distance as that between the Count's map and my own. We have no doubt erred in opposite directions, and the truth lies somewhere between us; but until some traveller takes a good chronometer up the river with a sextant for determining local time, or a telescope of sufficient size to observe eclipses of Jupiter's satellites, the true length of the river will not be settled.

In one of the latest atlases, "The Twentieth Century Citizens' Atlas," by Bartholomew, the position of the Jurupari fall is 62 per cent. further from the mouth of the river than on Stradelli's map, which seems to show either that some other traveller has determined the longitude, or that they consider my distances more correct than his.

Another traveller, Dr. T. Koch, only last year (1904) ascended the Uaupés to beyond the Jurupari fall, and also went up the Codiary branch where he reached an elevated plateau. But it is not stated whether he made any observa

tions to determine the true positions of his farthest point. (The Geographical Journal, July, 1905, p. 89.)

It seems probable, therefore, that the upper course of this great river for a distance of two or three hundred miles is quite unknown. But this is only one indication of the enormous area of country in the central plains of South America, which, except the banks of a few of the larger rivers, is occupied only by widely scattered tribes of Indians, and is as absolutely unknown to civilized man as any portion of the globe. From the Meta river on the north, to the Juambari and Beni rivers on the south, a distance of about twelve hundred miles, and to an equal average distance from the lower slopes of the Andes eastward, is one vast, nearly level, tropical forest, only known or utilized for a few miles from the banks of comparatively few of the rivers that everywhere permeate it. It is to be hoped that in the not remote future this grand and luxuriant country will be utilized, not for the creation of wealth for speculators, but to provide happy homes for millions of families.

As my collections had now made my name well known to the authorities of the Zoological and Entomological Societies, I received a ticket from the former, giving me admission to their gardens while I remained in England, and I was a welcome visitor at the scientific meetings of both societies, which I attended very regularly, and thus made the acquaintance of most of the London zoologists and entomologists. I also went frequently to examine the insect and bird collections in the British Museum (then in Great Russell Street), and also to the Linnæan Society, and to the Kew Herbarium to consult works on botany, in order to name my palms.

After discussing the matter with some of my friends, I determined to publish, at my own expense, a small popular volume on the "Palms of the Amazon and Rio Negro," with an account of their uses and distribution, and figures of all the species from my sketches and specimens of fruits. I arranged with Mr. Walter Fitch of Kew, the first botanical artist of the day, to draw them on stone, adding a few