Since I wrote the above notice of the _Curare_, or _Urari_, as the plant and poison were called by Raleigh, the brothers Robert and Richard Schomburgk have rendered important service to science by making us accurately acquainted with the nature and mode of preparing this substance, which I was the first to bring to Europe in any considerable quantity. Richard Schomburgk found this creeping plant in flower in Guiana, on the banks of the Pomeroon and Sururu, in the territory of the Caribs, who are, however, ignorant of the mode of preparing the poison. His instructive work[HW] gives the chemical analysis of the juice of the _Strychnos toxifera_, which, notwithstanding its name and organic structure, contains, according to Boussingault, no trace of strychnine. Virchow’s and Münter’s interesting physiological experiments show that the curare or urari poison does not appear to destroy by resorption from without, but chiefly when it is absorbed by the animal substance after the separation of the continuity of the latter; that curare does not belong to tetanic poisons; and that it especially produces paralysis, _i.e._, a cessation of voluntary muscular movement, while the function of the involuntary muscles (as the heart and intestines) continues unimpaired.[HX] ON THE CATARACTS OF THE ORINOCO, _Near Atures and Maypures_. In the preceding section, which I made the subject of an Academical Lecture, I have delineated those boundless plains, whose natural character is so variously modified by climatic relations, that what in one region appear as barren treeless wastes or deserts, in another are Steppes or far-stretching Prairies. With the Llanos of the southern portion of the New Continent, may be contrasted the fearful sandy deserts in the interior of Africa; and these again with the Steppes of Central Asia, the habitation of those world-storming herdsmen, who, once pouring forth from the east, spread barbarism and devastation over the face of the earth. While on that occasion (1806), I ventured to combine many massive features in one grand picture of nature, and endeavoured to entertain a public assembly with subjects, somewhat in accordance with the gloomy condition of our minds at that period, I will now, confining myself to a more limited circle of phenomena, pourtray in brighter tints the cheerful picture of a luxuriant vegetation, and fluvial valleys with their foaming mountain torrents. I will describe two scenes of Nature from the wild regions of Guiana,—ATURES and MAYPURES, the far-famed CATARACTS OF THE ORINOCO,—which, previously to my own travels, had been visited by few Europeans.