LOW LIFT PUMPING MACHINERY. LXXIII. 
charging into the suction of the second. An improved form of 
conjugate pump is shewn in Figure 8, which is taken from a paper 
by Mr. Richards on “Trrigating Machinery on the Pacific Coast.” 
With large diameter fans, unless for large quantities of water, 
the opening between the sides becomes very small so that it is not 
practicable to use them, and there is besides the extra skin friction, 
for taking the sizes given above 7/4 D? x W is for the 5’ fan 697 
greater than for the 3’ fan, and the friction of the rotating discs 
is almost three times as great for the large fan as for the small 
one. The use of two pumps or two fans in one casing naturally 
very considerably reduces the efficiency of the pumps, a test made 
with one on a lift of 36’ only shewed an efficiency of 43:6'/, in 
the author’s opinion it is not advisable to use centrifugal pumps 
for a greater height than 40’, and then only when the quantity of 
water is such as to enable the mouth of the fan to be not less than 
zy the diameter in width. 
The direct acting reciprocating pumps are well known, and as 
shewn in Figure 1, their efficiency is high, the author is aware 
of only one reliable test of these pumps, made when working 
on lifts of less than 25’ and that is of the great pumps used 
for draining Haarlem Meer in Holland, which on a lift of about 
16’ gave an efficiency of 70%, but judging from the experiments 
made with flywheel reciprocating pumps the efficiency will fall 
below that of centrifugal pumps, at about 25 to 30’, they have, 
however, the advantage over the latter in that, if required, small 
quantities of water can be raised by a pump whose normal duty 
is much greater. 
In direct acting pumps are included the ordinary Cornish beam 
engines, as well as what are more commonly termed direct acting 
pumps. | 
The non-compound direct acting pumps with the exception of 
the Cornish and Davey pumps, are very properly classed as steam 
eaters, but no engineer would think of using them for permanent 
1 Proceedings Inst. M.E., 1886, 
