On the Value of Water as a Moving Power . 171 
stal ; and cannot help regarding the objections stated on this oc- 
casion by Mr Chapman, as destitute of any solid support *. 
The facility of erecting a steam-engine almost on any spot, 
seems to have diverted the public from attending to the vast uti- 
lity of steady water-falls. The action of what is called a twenty • 
horse power engine , is just equal to the impulse given by 1000 
cubic-feet of water falling in a minute through the height of 
10 feet. But the yearly cost of an engine of that dimension is, 
under the most favourable circumstances, estimated at L. 1000; 
which is, therefore, the annual saving procured by such a fall of 
water. The perpendicular height of the proposed reservoir 
above the sea, we found barometrically to be 884 feet ; estimat- 
ing the quantity of discharge by the Water of Leith wdien full, 
at 1200 cubic-feet every minute. The whole force thus evolved 
by the descending stream, if rightly husbanded and directed, 
would be equivalent to the action of 106 steam-engines of twenty 
horse-power. The annual value of the different falls that could 
be procured along the river, when equalised throughout the year, 
by the supplies furnished in the dry season from the reservoir, 
must amount at least to L. 106,000. But this large saving or 
income is not merely advantageous to the proprietors of machi- 
nery established in the vicinity of our northern metropolis, but 
would contribute most materially to the wealth and prosperity of 
the country. It would create, for the use of the State, as great 
a store of labour as could be produced by the annual expendi- 
ture of half a million. An object, therefore, of such vast mo- 
ment, seems to claim the special patronage of the patriot and le- 
But the Water of Leith is to be considered as only a moun- 
tain-stream, and, therefore, liable to very great inequalities. Its 
whole annual discharge might be furnished from a surface of 
twenty square miles. The lower part of the current receives 
few feeders ; and the main supply of water is derived from a 
moorish tract of about fifteen square miles on the south side of 
the Pentland Hills. The sudden melting of snow, or a heavy 
fall of rain on these grounds, will sometimes send down, in a 
* Mr Chapman, in a printed report, maintains, that the erection of a reservoir 
in the course of the Water of Leith, would prove highly detrimental to the Harbour 
of Leith ; while Messrs Stevenson and Burstal are of opinion, that the operation 
of the water of such a reservoir would prove most beneficial to the Harbour. — Edit, 
