546 Trials of Traction- Engines at Wolverhampton. 
per horse-power per hour. It evaporated 7-76 lbs. of water per lb. of coal 
consumed. The indicator diagram, of which a copy is given below, shows 
Fig. 10. — Indicator Diagram of Messrs. Aveling and Porters G-Horse- 
powcr Locomotive, icith Internal Indiarnhhcr Tyres, No. 7003, 
the gross indicated horse-power to be 17"6, and the consumption of coal there- 
fore to be 3'77 lbs. per hour for each such horse-power. The oil and tallow 
used were 2 lbs. lOj ozs. ; but this large quantity was entirely due to a bearing 
having been suffered to become hot ; and as the ran could not be stopped to 
cool the bearing, excessive lubrication had to be kei)t up. The temperature 
of the feed water averaged about 130". 
Howcmrs 10-IIorse-poiocr, with Snfcfy Boiler. — The 3rd Group, that of the 
Howard Safety Boiler, with rigid ii-on wheels, comprised only one entiy, viz. 
Messrs. J. and F. Howard, of Bedford, No. 1170, price 410?. This is a 
10-horse-power engine, single cylinder, having a length of stroke of 1 foot, and 
a diameter of cylinder 10 inches, giving the exact Bmy standard of 10 circular 
inches per horse-power. 
This engine is provided with one of Howard's safety boilers, and was declared 
to work at 180 lbs. pressure. Tliis boiler consists of five vertical rows of tubes. 
The centre three rows are each composed of a nearly vertical pijje of a D shape 
when viewed in plan, having the flat side of tlie D towards the front side of 
the engine. From this fiat side, six nearly horizontal pipes, 9 inches in 
diameter outside and 5 feet long, extend towards the front of the engine. 
The two outer sections are also made of D pipes and horizontal pipes, but in 
• their case the horizontal pipes are only 7 inches outside diameter, and just touch 
each other as they lie one above the other ; while with the three inner sections 
there is a space of 1 inch between the jiipcs. There is a brass connecting-pipe 
which joins to one another the forward end of the horizontal pipes nearest but 
one to the bottpm of the boiler, and whicli serves for a feed connection. At 
the hinder end there is a somewhat similar connection for the steam. All 
these pipes are contained within a waggon-shaped casing. The spaces, such 
as they are, between the pipes of the outer rows are filled with fire-brick. At 
tlie bottom of the casing a fireplace is provided, and below that the ash-pan. 
Thus it will be seen that the fire plays up among the rows of tubes. It is not, 
however, permitted to go straight up through them, as there are cast-iron bars 
put in, which cause it to pass in a tortuous direction in ascending. The upper 
part of the case is made double, to witlistand the heat, and the chimney is 
mounted upion the middle of the top of the case. The upper horizontal tubes 
