PROCEEDINGS OF SECTION H. 367 
1. Make the reciprocating parts of the engine as light as 
possible. The writer is of opinion that more could be done in 
this direction than has been hitherto by the use of high-class 
material and careful scientific design of pistons, rods, and cross- 
heads. 
2. Do not attempt to fully balance these parts. Be content 
with a palliative treatment, in which from one-half to three- 
fourths of the reciprocating parts are balanced, the lower propor- 
tion being taken when the permanent way is known to be weak, 
and it is desired to spare it as much as possible, even <t the 
oe of rather more fore and aft jerking. 
. Divide the balance weights required for the reciprocating 
en between all the coupled axles equally. In this way the 
injurious vertical force at any one axle is rendered as small 
as possible, though this is at the cost of somewhat increased 
pressure on axle boxes. 
In the above way the very successful results reported by 
Mr. Woodroffe were obtained. The engines were six coupled 
inside-cylinder locomotives, having each axle in mathematically 
perfect balance as regards the revolving weights, and each of 
the axles balanced for one-fourth of the reciprocating parts, 
all the separate balance weights required for various purposes 
in each wheel being combined into one resultant balance weight, 
placed at as large a radius as the size of the wheel permitted. 
The critical speed of these engines, or the speed at which 
the wheels would begin to hammer the rails, is shown by cal- 
culation to be between 150 and 200 miles per hour, and, there- 
fore, immeasurably beyond the possibilities of ordinary work, 
which may be put at about 40 miles per hour. 
The above represents the best that can be done with ordinary 
two-cylinder locomotives. In some _ places, however, four- 
cylinder compound locomotives, having outside high pressure, 
and inside low pressure cylinders, are coming into use; here 
the outside piston travels forward, wlile the inside adjoining 
one moves backward, and the two balance each other in a most 
efiective way. Such engines ought to run with great smooth- 
ness at very high speeds, and they are reported | to do so on 
the Northern Railw vay of France, where they are in use. The 
only remaining defect in these engines, and it is probably im- 
perceptible, should be a slight lateral movement, due to the: 
fact that the two adjoining pistons are not moving in the same 
vertical plane. If necessary, this could be met by the adop- 
tion ot the Yarrow-Schlick-Tweedy arrangement of cranks that 
has proved so excellent in torpedo boats. This would merely 
involve moving the cranks a few degrees away from their pre- 
sent position at 90 deg. apart. We should then have a locomo- 
tive in almost perfect balance. 
