RESIDENCE AT SANTAREM iii 
could scarcely be less than from 20 to 30 feet thick. 
All the nodes, save three or four of the uppermost 
ones that were above water, sent out rootlets, 
doubtless to extract subsistence from the water ; 
and several of the lowest internodes were dead and 
half-decayed ; yet nearly all the stems bore vigor- 
ous panicles of flowers, so that at a short distance 
the island resembled a luxuriant meadow. Float- 
ing on the water, and kept in by the grass-stems, 
were several minute plants : an Azolla, two Salviniae, 
a small Pistia, and an undescribed Frogbit {Hydro- 
cha7^ella chcetospora, gen. nov.) ; besides several small 
molluscs. 
Sometimes the voyager finds refuge from a 
squall by forcing his canoe into the yielding mass 
of a Grass-island, which breaks the shock of the 
waves ; but when the river is rising rapidly, float- 
ing islands oblige the pilot to keep a sharp look-out, 
especially by night, and in the wet season no vessel 
anchors in the Amazon : the least evil that could 
result from such imprudence would be the dragging 
of her anchor by the onslaught of a Grass-island. 
From what has been said above of their bulk, and 
also taking into account that the winter current of 
the Amazon is at the rate of four or five miles per 
hour, some idea may be formed of the effect of their 
meeting a vessel stemming the stream, or even 
anchored in it, and there have been instances of 
vessels getting half-buried, and sometimes swamped, 
in the floating mass. In 1836, the year following 
the rebellion of the Cabanos, five sloops of war 
were sent from Para to receive the submission of 
the various towns on the river, and whilst lying at 
anchor in the port of Santarem, a Grass-island of 
