650 MR E. M. WEDDERBURN 
the depth of 16 metres is shown by a horizontal line. The next diagram (fig. 19) shows 
the density and viscosity distribution, corresponding to the mean temperature distribu- 
tion, the depth of 16 metres being again marked by a horizontal line. The density 
gradient from 15 metres to 18 metres is pretty uniform, and, for the purposes of 
calculation, 16 metres was taken as the depth of the boundary. If the suggestion made 
in page 648 were carried out, the depth would have been taken at 15 metres; but as the 
difference in viscosity between 15 metres and 16 metres was so slight, there did not 
seem to be much justification for taking a less depth than 16 metres. 
The next step in the calculation was the construction of the o (v) curve for the loch, 
and this was rather a laborious process. Cross sections were drawn for each point at 
which a sounding line had been made by the lake survey—-28 in all—and the breadth 
of each cross section, at depths at intervals of a metre, was tabulated. By summing 
Fig, 20.—o (v) curve and biparabolic approximation. 
the breadths thus tabulated a good approximation to the areas of the cross section 
above and below the boundary was obtained, and from this TST was calculated. 
Each breadth was then multiplied by the difference in density of the water at that 
depth, and at the depth of the succeeding metre. By summing the values so obtained, 
an approximation to 2p’,b’,(x) + 2p,b,(x) was obtained for each cross section. 
The area, measured by planimeter along a 16-metre contour line drawn on the map, 
between successive cross sections, was then plotted against the values obtained for 
1 Ls 
cinerea the resulting curve, shown in fig. 20, being analogous to Professo 
N(@) * A@) 
CurRYSTAL’s seiche o(v) curve. 4 
The method of least squares was employed to obtain an approximation to this curve 
by means of two parabole, just as was done by Professor Curysrat and the author* in 
the case of ordinary seiches in Loch Harn. The details of the calculation are shown in 
the following table :— 
, 
d 
P 
r 
* Trans. Roy. Soc. Edin., xli, (iii.) p. 823. 
