Trials of Traction-Engines at Wolverhampton. 
541 
cases, testing by tlic (lynamouietcr-brake is not, and, in fact, could not be 
aiiplied ; the power, therefore, which is reported is invaiiably, in the case of 
marine engines, the gross indicated horse-power, and the consumption of fuel is 
referred to this gross indicated horse-power ; and certainly, now that the corn- 
Fig. 6. — Indicator Diagram of Messrs. Aitling and Porter's 10-Rorse- 
jiouer Loeoniolicc, No. 7001. 
parison can be made, the agricultural engineers may be well satisfied to find 
their non-condensing engines working down to, if not below, the average 
consumption of extremely good condensing engines in the navy. Ko doubt this 
excellent result is largely due to the fact of the exhibitor being permitted 
to work at a really high pressure. It cannot be too constantly urged upon 
engineers and upon users of engines that the employment of a low pressure 
in non-condensing engines is an extremely wasteful thing ; yet, clear as this 
is or should be to an engineer, the users of engines certainly do not recognise 
the truth of the proposition, as one may hear a man boasting, " I have got an 
extremely good engine (a non-condensing one) : she will drive the whole of 
her w-ork with 30 lbs. steam ;" never retiecting that when he is using steam 
at only 30 lbs. above atmospheric pressure in a non-condensing engine, one- 
third of the whole of the fuel is consumed in getting the steam up to the 
atmospheric pressure ; while if he were to use the steam at 120 lbs. to the 
inch, only one-ninth of the fuel would be so wasted. 
Before proceeding to relate the next trial to which this and the other 
engines in Class XA'^II. were subjected, it will be well probably to describe 
those other engines, and to state their pierformances on the brake. 
Avding and Porter's Q-Horse-poiver, Ko. 7002, I'rice 300?. — This engine 
is generally similar to their engine No. 7001, already described. The principal 
points of difference are that the steering-wheels are wood ; that the driving- 
wheels, which are 5 feet diameter and 10 inches wide, have wrought-iron 
tyres, with strips of wrought iron riveted on angleways; that the feed-pump 
regulation is made by a cock in the suction-pii^e ; that the reversing-handle 
is not provided witli a screw adjustment, and that there is not any brake. 
The boiler of this engine contains 28 tubes, of 2h inches outside diameter. The 
fire-grate has an area of 4 33 feet, and there is a total heating surface of 
106 feet and a flue-area of '534 foot. The diameter of the cylinder is 
