38 
BATHYMETRICAL SURVEY OF 
Cubic feet. 
50 to 
60 inches, 
3 ’79 square 
miles X 
55 inches 
= 484,272,000 
60 ,, 
70 „ 
23-89 
X 
65 „ 
= 3,607,591,000 
70 „ 
80 ,, 
21 -79 
X 
75 „ 
= 3,796,700,000 
80 „ 
90 „ 
19-02 
X 
85 ,, 
= 3,755,928,000 
90 „ 
100 „ 
441 
X 
95 „ 
- 973,307,000 
100 „ 
110 ,, 
0-49 
•X 
105 „ 
- 119,530,000 
Total 
The 
thus : — 
12,737,328,000 
results obtained by these three methods may be summarized 
First method 
Second ,, 
Third ,, 
Mean 
Vennacliar catchment. 
14.857.214.000 
14.991.815.000 
12.424.867.000 
Lubnaig catchment. 
15.600.760.000 
15.750.446.000 
12.737.328.000 
14,091,299,000 c. ft. 
14,696,178,000 c. ft. 
Since Loch Katrine has been made use of by the Glasgow Corpora- 
tion as the source of the water-supply to that city, a record has been 
kept of the amount of water flowing out of Loch Vennacliar — or rather, 
a record has been taken twice a day of the depth of water flowing over 
a weir at Coilantogle, from which the quantity of water discharged may 
be calculated. When the height of the water on the weir exceeded 5 
inches, the weir became a drowned weir, so that it was difficult bo 
estimate the outflow, as there was a considerable velocity of approach, 
especially during floods. 
Mr. Gale has kindly supplied us with the readings, taken twice a 
day during the year 1869, of the depth of the outflowing water at 
Coilantogle, and from these figures the outflow has been estimated for 
that year at 9,572,000,000 cubic feet. The year 1869 was the driest 
year during a period of twenty-four years, and we are not satisfied that 
this computation can be accepted as a very correct estimate of the out- 
flow from this catchment-basin even for that year. It would have been 
interesting to have calculated the outflow for twenty-five years in the 
same way as we have done for the year 1869, and to have taken the 
mean. However, accepting the above estimate for the year 1869, and 
adding to it the quantity of water supplied to Glasgow for that year, 
which, from Mr. Gale’s table showing the average amount of water 
supplied per day during the first six months of the years 1866 and 1871, 
may be taken at about 1,659,300,000 cubic feet, we find that the mean 
rainfall exceeds the outflow in this year by 
According to the first method ... 
., ,, second ,, 
third ,, 
3.625.914.000 cubic feet. 
3.760.515.000 
1.193.567.000 
Or a mean of ... ... 2,859,999,000 ,, 
Leslie* made experiments for twenty consecutive years on the 
See Jour. Scot. Met. Soc., vol. v. p. 108, 1878. 
