SEICHES AND OTHER OSCILLATIONS 
59 
with any degree of accuracy. Both these causes introduce uncertainty 
in the method of observing with index hmnographs on two sides of 
the node where the seiche is found in opposite phases, and then 
deducing its position by interpolation. A mere null method would 
scarcely lead to a satisfactory result, unless under exceptional 
circumstances which did not occur during the observations. Of the 
many attempts made, only a few led to limnograms which could 
be utilised ; and in every case the curves had to be purified by 
residuation. 
Uninode. — The two best pairs of observations gave almost exactly 
the same position for the southern end of the uninode, and led to the 
conclusion that it lies about 105 yards west of the position given in 
the paper on the Calculation of the Periods and Nodes of Lochs 
Earn and Treig. This is precisely what was expected, as the actual 
normal curve (C.P.N. , p. 825) rises above the assumed biparabolic 
curve on the west and falls below it on the east of the calculated 
position of the uninode. It would be useless to calculate what the 
amount of divergence ought to be, because the uncertainty of one of 
these determinations, as shown by the observations themselves, is ±65 
yards, and of the other ±129 yards, the latter being more than the 
divergence itself. The exact agreement of the two determinations is 
probably an accident. 
Eastern Binode. — Two determinations agreed almost exactly in 
placing the Eastern Binode about 117 yards west of the calculated 
position ; but the uncertainty of these determinations was ±94 
yards in the one case and ±59 yards in the other. 
Western Binode. — The best pair of observations gave a position 
for the southern end of the Western Binodal line 305 yards west of 
the calculated position. A divergence in this direction was to be 
expected from the shape of the true normal curve in the neighbour- 
hood, but the amount is somewhat surprising. There can be little 
doubt of the correctness of the observation, because it was confirmed 
by another pair of observations, one made almost exactly at the 
position above indicated, the other 250 yards farther east. The 
latter gave on residuation a well-marked binodal seiche, the former 
none that could be recognised. 
Eastern Trinode. — The best observation available places the 
southern end of the Eastern Trinodal line 88 yards west of the 
calculated position. The uncertainty of the determination, however, 
exceeds 120 yards, so that it cannot be said for certain whether the 
actual trinode is really west or east of the calculated position ; from 
the shape of the normal curve we should expect a considerable 
divergence to the east. 
Middle Trinode.— Unfortunatelv the observations for the de- 
