At the western end of the Mare aux Vacouas is an outlet through which a constant stream flows, and this is the commencement of the principal branch of the R. du Tamarin; the other branch, called the R. des Aigrettes, is said to take its rise near a more distant lake, named the Grand Bassin; and their junction is made about one mile to the S. S. W. of the Refuge, near the boundary ridge of the high land, through which they have made a deep cut, and formed a valley of a very romantic character. A short distance above their junction, each branch takes a leap downward of about seventy feet; and when united, they do not run above a quarter of a mile northward before they descend with redoubled force a precipice of nearly one hundred and twenty feet; there are then one or two small cascades, and in a short distance another of eighty or a hundred feet; and from thence to the bottom of the valley, the descent is made by smaller cascades and numberless rapids. After the united stream has run about half a mile northward, and in that space descended near a thousand feet from the level of Vacouas, the river turns west; and passing through the deep cut or chasm in the boundary ridge, enters the plain of Le Tamarin and winds in a serpentine course to the sea.
The R. du Tamarin is at no time a trifling stream, and in rainy weather the quantity of water thrown down the cascades is considerable; by a calculation from the estimated width, depth, and rate of the current after a hurricane, the water then precipitated was 1500 tons in a minute. There are some points on the high land whence most of the cascades may be seen at one view, about a mile distant; from a nearer point some of them are perceived to the left, the Trois Mamelles tower over the woods to the right, and almost perpendicularly under foot is the impetuous stream of the river, driving its way amongst the rocks and woods at the bottom of the valley. In front is the steep gap, through which the river rushes to the low land of Le Tamarin; and there the eye quits it to survey the sugar plantations, the alleys of tamarinds and mangoes, the villages of huts, and all the party-coloured vegetation with which that district is adorned; but soon it passes on to the Baye du Tamarin, to the breakers on the coral reefs which skirt the shore, and to the sea expanded out to a very distant horizon. An elevation of ten or eleven hundred feet, and the distance of three or four miles which a spectator is placed from the plantations, gives a part of this view all the softness of a well-finished drawing; and when the sun sets in front of the gap, and vessels are seen passing before it along the coast, nothing seems wanting to complete this charming and romantic prospect.