274 
Water Mills. 
there is a serious loss of power, but more especially so where it 
consists of a few feet only. The patentee has satisfactorily prov- 
ed, that with a head and fall of twelve feet, six feet of back water 
maybe driven away, and with it, all the water which has been ex- 
pended in moving the wheel : there is therefore, no exaggeration 
in declaring, that taking into the account th£ time that many mills 
are stopped by back water, and the permanent loss of power from 
the height at which the wheels are hung in order to avoid this 
difficulty ; from one fifth to one third of the power is absolutely 
lost, an evil which is completely obviated by this invention. 
All the time when the wheel is retarded'by back water, a large 
quantity is constantly running to w r aste ; this invention accom- 
plishes its removal by the application of a portion of this super- 
abundant water, which would otherwise run over the daim 
The above section will shew the operation of this principle in 
removing back water; The construction of the doom, and race- 
way, differs from the common form, by having a tight tube, A, 
running from the bottom of the floom, as at D, to or past the cen- 
tre of the bottom of the wheel, and of about four times the size of 
one which would be necessary to turn the wheel. The size of the 
tube may vary according to the back water common to the mill. 
The lower end of the main tube, A, being in a direct line to that 
of the horizontal tube, B, will direct the water which rushes down 
the former through the latter, and at the same time overcome the 
pressure of the water and atmosphere at C, so that the atmos- 
phere may act upon the back water which had collected round the 
bottom of the wheel, and force it through the tube, B, which 
being one third larger than tube A, will admit enough of the back 
water at the opening, F, to fill the tube B, and thereby in a few’ 
minutes, to entirely remove it from the bottom of the wheel ; and 
the water which has been expended in moving the wheel, will join 
the current at F, and pass off through the tube B. The bulk-head, 
G, must rise above the extreme height of the back water, for as 
there is no other passage for the water to escape from the wheel, 
than through the tube B, there should be no other through which, 
in times of backwater, it can pass to the wheel. When the freshet 
is over, and the water has found its lowest level, the horizontal 
gate, D, should be shut, and the water which carries the wheel 
will run off through the tube B. 
This method of removing back water, will not apply to tide 
mills, except where there is a great surplus of water; in that ease, 
by adopting this plan, the mill may be made to go sooner and later 
