144: REPORT—1874. 
the Cusher river. Of this 166 feet 7 inches, 155 feet 4 inches are rated at 
£10 per annum per foot fall, and 11 feet 3 inches at £5. Linen Hill and 
Ardbrin falls are also rated at £5, and make the total income £1675 8s. 4d. ; 
but £224 11s. 8d. must be deducted from this for four falls unoccupied at 
present, leaving a net sum of £1450 16s. 8d. For so far the undertaking has 
not paid the shareholders well, as the expenses connected with the Muddock 
river sometimes absorbed the entire dividend ; latterly, however, the dividend 
has amounted to above 3 per cent.; and if the present litigation was favour- 
ably settled and the falls more fully occupied, a fair return may be expected. 
The recent material advance in the price of fuel and the expected opening of 
the Banbridge Extension Railway should contribute to this end. 
Lough Island Reavy reservoir has now been worked for thirty-four years, 
and has well borne out Sir William Fairbairn’s anticipations of its utility in 
impounding water and giving out a supply to the mills. In his calculations, 
as no extended rainfall observations had been made in that district, he 
assumed the rainfall as 36 inches, which was the average for the whole of 
Ireland. He deducted one sixth of the rainfall for absorption and evapora- 
tion, and concluded there would be sufficient left to fill the reservoir once 
and a quarter, on the average, in the year. I have, however, maintained 
a rain-gauge at Lough Island Reavy since May 1861, and find the average 
fall at a level of 6 feet above the top water of the reservoir is 46 inches. 
That amount over the five square miles drainage-area of the lake yields 
535,000,000 cubic feet, and the capacity of the reservoir filled to 38 feet 
6 inches above the outlet is 270,000,000 cubic feet. A rainfall of 23 inches, 
if there were no loss, would fill the reservoir; but it requires about 30 inches 
to do so from the beginning of October till that of April (the season it is 
generally filled), and the evaporation during the other six summer months is 
about four times as much. We may therefore assume the loss to be about 
one third the whole rainfall, leaving sufficient to fill the reservoir one and 
one third times. The rainfall must be greater on the high ground than at 
the gauge, so that only one half the whole rainfall is probably available. 
The Butter Mountain, from which most of the drainage is derived, is peaty, 
which will account in some measure for the large amount of absorption on 
such steep ground. It is also to be remembered that the evaporation from 
the surface of the reservoir is very great. At the intake of the Corbet reser- 
voir, where the drainage from eighty square miles of mixed flat and moun- 
tainous country passes down the river Bann, I found, on comparing the 
quantity passed over Ervin’s Weir with the average rainfall for the year 
1872, the former to be only one fifth the latter, equal to a loss of four fifths 
the rainfall by evaporation and absorption. This calculation can only be 
taken as an approximation, since Eryin’s Weir is not constructed for accurate 
gauging, and I was obliged to deduct 20 per cent. from the calculated dis- 
charges as a rough estimate of the loss from the absence of a level ridge 
board and the broad and irregular surface of the weir; besides, to obtain an 
accurate idea of the amount of rainfall, returns should be obtained from a 
number of gauges well placed over the varying surface of the country. This 
inquiry as to the relative amount of rainfall and absorption in yarious 
districts of country is very interesting, and more information on the subject 
is desirable. . 
A register of the daily height of the water in Lough Island Reavy has been 
kept since 1847 by the caretaker. It shows that this reservoir has been of 
great service to the mill-owners on the Upper Bann, as during twenty-six 
years an average supplementary supply of about two fifths of the standard 
