430 
DES, T. ANDEESON AND J. S. FLEET OX THE EEUPTIOXS OF THE 
hot ash. They were bounded towards the river by sharji slopes, from 1 foot to 10 
or 12 feet high, by which the surface descended from one terrace to another, and little 
landslips frequently took j^lace as the loose material dried after rains and tumbled 
down the bank upon the terrace beneath (see Plate 29, fig. 2). They were not, as a 
rule, equally numerous and well-developed on both sides of the stream ; commonly 
on one side there was a vertical cliff, while on the other several terraces might be 
seen. Traced down the stream few of them extended for more than 70 to 100 
yards, and they were l)est seen during the last mile of the river s course, where it 
runs on the south side of the flat-topped ridge behind Wallibu estate. 
Tlie origin of these terraces is not difficult to explain. Immediately after the 
eruption the valley was more or less completely filled with fine hot ash, mixed with a 
certain proportion of coarse blocks and bombs. The river when it resumed its flow 
found it a matter of no great difficulty to wash out or re-arrange this material. But 
the rains in St. Vincent are intermittent, and take the form of heavy showers, during 
which the streams come down in flood and frequently are raging torrents. At other 
times the quantity of water in their channels is very small, though this stream was 
never quite dry in the month of June wlien we saw it. A small l)ody of water, black 
as ink and thick with mud, was always flowing to the sea, steaming strongly and very 
liot. It came in gushes which rushed down with a wave in front of them (see 
Plate 23, fig. 2), several inches or a foot in height, and l)etween these the current 
was very slight and, in fact, almost ceased. It was not liot water but black boiling 
mud, and the stronger rushes carried with them pebbles several inches in diameter. 
On one occasion, when we were returning from an ascent of the mountain, we found 
one of the smaller streams, which we had crossed dryshod in the morning, so swollen 
l)y heavy showers that it was flowing in a thick black current 2 or 3 feet deep and 
several yards across. It was very hot, and we had to cut down some of the bare tree 
trunks to form a temporary bridge. Not long after we had crossed, this was carried 
away by the current. 
This thick muddy flow constantly bears much material to the sea. The banks 
of ash on each side frequently slip down, especially when the hot sand dries after rain, 
and wlien it is undermined by the stream, and little landslides take place which 
temporarily dam back the current till the pressure of water increases and sweeps 
away the obstruction. Hence the intermittent flow and gushes of hot mud. A 
process of gentle erosion constantly goes on in which the river, unable to deepen its 
channel rapidly, keeps widening it by undermining the banks on each side and 
carrying away the material precipitated into the stream. 
But after rains the magnitude and velocity of the current are greatly increased, 
and its cutting power so enhanced that it trenches deep grooves in the ash filling its old 
channel. According to our observations the increase of depth may amount to several 
feet in an hour, so soft is the recent ash and so rapid and powerful are the torrents 
When the shower is over the flood subsides almost as rapidly as it rose, and the 
