16 ANNIVERSARY ADDRESS. 
Glover, who has charge of the gauge, saw a thunder-storm coming 
down from the north, and went into the recording-house to see its 
effect. The lake was rising fast, and in thirty minutes rose 4 inches. 
As the storm passed overhead the rising ceased, and the lake at once 
began to fall, getting back to its previous level in fifteen minutes; 
passing this point it fell 2 inches more—in all 6 inches—and then 
began to rise again, so starting a series of pulsations that lasted 
five days. Rain came with the storm, and on the 14th and 15th, 
measured by gauges at each end of the lake, 1:10 inch rain fell, and 
this caused a rise of 14 inch in the lake, which can be distinctly 
seen in the record as something independent of the pulsations. 
With the rain there was a strong breeze of wind, and, by the third 
day after, the water had returned to its old level, all the rain 
,having evaporated in three days. In each of the cases I have 
mentioned so far the impulses seem to have been given by a 
sudden storm breaking over the lake, but there are other instances 
in which the impulse was of a totally different character, and it 
seems as if a small force properly managed was made to do duty 
for a large one, just as we set a heavy weight suspended by a 
string in motion by giving it first a little push, and then adding 
impulse to each swing. So the force, whatever it be, which in 
these cases acts on the water in the lake, gives it a little start and 
gradually gets itin motion. The best instance of this occurred on 
the afternoon of April 5th. At the time the lake was very quiet, 
and suddenly the water rose an inch, and fell again within thirty 
minutes ; next time it rose an inch and a half, and fell 2 inches in 
three-quarters of an hour ; the next time it rose 2 inches, and fell 
34 inches in an hour ; it then rose 3? inches in forty minutes, and 
so started a series of pulsations which settled down to two-hour 
intervals, and lasted twenty hours. Usually the rise and fall take 
about equal times, but now and then the whole fall will take place 
in fourteen or fifteen minutes and the corresponding rise take 116 
minutes, and it is not very unusual to find one in a set of twice 
the period of the others, as if one had been left out; in fact the 
variations in the conditions of vibration are very puzzling. With 
a view of finding out the most common period, I have measured 
