April 20.--We travelled in a N. 80 degrees W. course to latitude 19 degrees 9 minutes 88 seconds. Rocky ranges frequently approached the river, and deep and intricate gullies descended from them to the latter. Our progress was consequently very difficult, and we were compelled to ascend a very high hill to avoid its slopes towards the river, which were too steep for us to cross. As a recompense, however, for the difficulty of the ascent, I had the pleasure of finding some very interesting plants on its summit; particularly a small Acacia with verticillate leaves, which Dr. Binoe, the surgeon of H. M. S. Beagle, had found on the north-west coast; and two other Acacias equally new to me, and which were afterwards found to extend to the heads of the South Alligator River. From this hill we had a magnificent view of the country before us: it was enclosed on all sides by high mountain ranges, of which one in particular overtopped the rest. Porphyry was observed on several spots; indurated clay frequently; and, on the top of the hill below which we encamped, I found quartz porphyry, and at the foot a psammite? which I had met several times associated with talc-schiste. April 21.--We continued our journey in a S. 50 degrees W. course to latitude 19 degrees 13 minutes. The country became still more mountainous; we passed, notwithstanding, many large well grassed flats, on which the timber grew to a greater size than we had observed it at the lower part of the river. The poplar-gum was very frequent in the hollow, and low stiff flats extended parallel to the river. The prevailing rock was talc-schiste, alternating with layers of psammite. On the hills and in the creeks, I frequently observed conglomerate, with many pieces of quartz. The drooping Hakea of Kent's Lagoon (Hakea lorea, R. Br.; Grevillea lorea, R. Br. Prodr. Nov. Holl. I. p. 380) was in blossom; and on the rocky slopes I found a new species of Hakea, having linear lanceolate leaves with axillary fascicules of small brownish flowers: it was an arborescent shrub, from three to six feet high; and is nearly allied to H. arborescens (R. Br. Prodr. p. 386). A high imposing range was visible to the northward.