THE FRESH- WATER LOCHS OF SCOTLAND. 37 
based upon the mean height, which gave a total annual rainfall of 
14,857,124,000 cubic feet. 
Applying the same method to the entire catchment-basin flowing 
out of Loch Lubnaig, we arrive at the following result: — 
Cubic feet. 
lochs to 500 feet, 6 ’82 square miles x 
74 ’6 inches 
:= 1,181,982,000 
500,, 750 ,, 
7T5 
„ X 
77-9 „ 
= 1,293,991,000 
750 „ 1000 ,, 
9-05 
,, X 
82-7 ,, 
= 1,738,769,000 
1000,, 1250 ,, 
9-70 
,, X 
87-4 ,, 
= 1,969,568,000 
1250,, 1500 ,, 
9-89 
,, X 
92-2 ,, 
= 2,118,434,000 
1500,, 1750 ,, 
9-43 
X 
97-0 ,, 
= 2,125,060,000 
1750,, 2000 ,, 
8-06 
,, X 
101-7 ,, 
= 1,904,337,000 
2000,, 2250 ,, 
6-64 
,, X 
106-5 ,, 
= 1,642,879,000 
2250 ,,2500 „ 
3-30 
,, X 
111-3 „ 
= 879,148,000 
2500 ,,2750 ,, 
1-88 
,, X 
116-1 ,, 
=r 507,081,000 
2750 „ 3000 „ 
102 
,, X 
120-8 ,, 
= 286,256,000 
Over 3000 ,, 
0-35 
„ X 
126-6 ,. 
= 102,941,000 
Total . . . 
15,750,446,000 
Here, again, there is a close agreement between the result obtained 
by this method and that calculated from the mean height, which gave 
a total annual rainfall of 15,600,760,000 cubic feet. 
A third method of estimating the amount of rain falling on any 
particular region is afforded by drawing lines of equal rainfall, measur- 
ing the areas between the lines, and multiplying by the mean annual 
rainfall. Where the lines are based upon sufficiently numerous records 
of rainfall at various heights, this method should give excellent results ; 
but in the cases under discussion the number of observing stations is 
small, and the majority of the rain-gauges are situated on the low-lying 
grounds, only two being placed at heights exceeding 1000 feet, both 
at 1800 feet : therefore the figures obtained in these cases are most 
probably below the truth. Nevertheless, we have attempted to lay 
down the lines of equal rainfall from the available records, as shown 
on the accompanying rainfall map (see Plate III.). The areas enclosed 
by the lines of rainfall have been measured with the planimeter, and 
the rainfall calculated for the Loch Vennachar catchment-basin, with 
the following results : — 
Cubic feet. 
50 to 
60 inches. 
12-35 
square miles 
X 
55 inches 
= 1,578,040 000 
60 „ 
70 „ 
28-97 
5? 
X 
65 „ 
= 4,374,714,000 
70 „ 
80 „ 
18-93 
? ? 
X 
75 „ 
= 3,298 372, 0(X) 
80 ,, 
90 „ 
8-55 
X 
85 „ 
= 1,688,400,000 
90 ,, 
100 ,, 
4-21 
? 
X 
95 „ 
= 929,166,000 
100 „ 
no ., 
2-28 
> ? 
X 
105 „ 
= 556,175,000 
Total ... 
12, 424, 867 poo 
In like manner, the rainfall has been calculated for the Loch 
Lubnaig catchment-basin, with the following results : — 
