return.  Had we been within distance, they would assuredly have hurled their spears at us.  Thirteen of them followed us to our resting place.  They kept rather apart from us, and kindled their fire in a little hollow about fifty paces to our right; nor did they venture to approach the tents unless we called to them, so that by their quiet and unobtrusive conduct they made up in some measure for the unruly proceedings of others of their tribe.

We had now arrived at a point at which I hoped to gain some information from the natives, respecting the sea.  It was to no purpose, however, that I questioned these stupid people.  They understood perfectly, by my pointing to the sky, and by other signs, that I was inquiring about large waters, but they could not, or would not, give any information on the subject.

Change in the geology of the country.

As we proceeded down the river, its current became weaker, and its channel somewhat deeper.  Our attention was called to a remarkable change in the geology of the country, as well as to an apparent alteration in the natural productions.  The cliffs of sand and clay ceased, and were succeeded by a fossil formation of the most singular description.  At first, it did not exceed a foot in height above the water, but it gradually rose, like an inclined plane, and resembled in colour, and in appearance, the skulls of men piled one upon the other.  The constant rippling of the water against the rock had washed out the softer parts, and made hollows and cavities, that gave the whole formation the precise appearance of a catacomb.  On examination, we discovered it to be a compact bed of shells, composed of a common description of marine shell from two to three inches in length, apparently a species of turritella.

Banks of petrified shells.

At about nine miles from the commencement of this formation, it rose to the height of more than 150 feet; the country became undulating, and a partial change took place in its vegetation.  We stopped at an early hour, to examine some cliffs, which rising perpendicularly from the water, were different in character and substance from any we had as yet seen.  They approached a dirty yellow-ochre in colour, that became brighter in hue as it rose, and, instead of being perforated, were compact and hard.  The waters of the river had, however, made horizontal lines upon their fronts, which distinctly marked the rise and fall of the river, as the strength or depth of the grooves distinctly indicated the levels it generally kept.  It did not appear from these lines, that the floods ever rose more than four feet above the then level of the stream, or that they continued for any length of time.  On breaking off pieces of the rock, we ascertained that it was composed of one solid mass of sea-shells, of various kinds, of which the species first mentioned formed the lowest part.