292 Scientific Proceedings, Royal Dublin Society. 
1894, a gale subsiding; so that there is some difficulty in under- 
standing in what manner the seiches occurring on those several 
days could have been influenced by wind. 
The barometer was not observed during the October seiches, but 
on all other occasions of their occurrence a low barometer was 
registered. 
II. What I would term the other class of seiches occurred 
frequently during the many heavy westerly gales of winter, at 
which time the level of the lake was being continually altered by 
rains, and the seiches then assumed a totally different character, 
the rise and fall being no longer slow and steady, the water 
rushing upon, and receding from, the shore in the form of waves. 
The gauge, situated on the weather shore, and in perfect shelter, 
showed these variations as a quick pumping, making observations 
of duration impossible, although nearly 6 inches of amplitude was 
frequently registered. 
Characteristics of the shores in the immediate neighbourhood 
of the spots where observations are taken, most probably govern 
both amplitude and duration of a seiche, but the duration so 
affected may be fairly constant at each station where observa- 
tions are taken, although the amplitude may differ considerably 
on different days.’ 
On referring to the accompanying plan of Lake Derravaragh, 
it will be seer that the observation spot is somewhat peculiarly 
situated as regards its surroundings: to the west and north-west 
the hills about Knockbody rise directly behind the house, and on 
the opposite side of the arm of the lake, at less than 400 yards 
distance, Knockross springs abruptly from the lake. To the 
south-westward of the house, the land becomes somewhat lower 
(about 100 feet above the lake) ; and in gales from that quarter, 
the wind, blowing across the lake, impinges on the steep side ot 
Knockross, and is deflected back on Knockbody (see dotted line) 
with such violence that it becomes, under those circumstances, a 
bad lee-shore fora boat. It will thus be seen that the observation 
spot is apparently contained in an approximate right angle, formed 
by the advancing and deflected wind. 
I have already alluded to the difficulties in obtaining complete 
1“ Take,” Eneyclopedia Britannica, 9th ed., vol xiv., p. 220. 
