400 
both localities (cf. Pl. IX. and XXXVI.) in the face of these 
contrasts in amplitude. 
1896. 
(Table VIII., Pl. XX XVII.) 
There were 27 collections in this year, at monthly inter- 
vals until April, and then every 5-1] days until the end of Au- 
gust, and thereafter every fortnight. The average production 
in this year is 9 em.’ per m.’, with a maximum at the vernal 
pulse on May 2 of 48.99 em.’ 
The hydrographic conditions of this year are such as to 
bring Thompson’s Lake into intimate connection with chan- 
nel waters. The average height of the river for the year, 6.98 
{t., is sufficient to maintain a run-off from the southern end of 
the lake to the river, submerging the bottom-lands between to 
the depth of a foot. Indeed a run-off of varying depths was 
maintained for 241 days, in which stages exceeded 6 ft. This 
was due to the recurrence of 6 floods, so distributed as to keep 
the lake discharging through the southern outlet for 241 days 
with only 5 interruptions between May and December. Of the 
125 days in which water did not flow through the lake from the 
northern to the southern end, there were 29 of rising water in 
which no discharge to the river occurred, 28 of stationary 
levels in which the movement of the water, if any, was declin- 
ing, and 68 of falling water, in which the lake discharged 
through the slough at the northern end. Thus, during 309 days 
of the year this lake was discharging to the channel, waters 
which had been impounded for a varying length of time within 
its boundaries. The importance of this impounding area is 
best shown by rough calculations which show that the run-off 
of a single foot from the lake proper, not including the expand- 
ing areas which join it with every rise in levels, will fill the 
channel of the river at Havana to a depth of 8 ft. (low-water 
stage) for about three miles. In 1896 the total depth of the 
run-off for the year computed on a single discharge after each 
