a i eee 
OF COAL AND RATE OF EVAPORATION. 25 
Fire-place 4 feet 8 inches by 6 feet, equal to 28 square 
feet. 
Fire-bars distant 12 inches at the front and 13 inches at 
the back from the bottom of the boiler. 
Bars half inch thick with half inch spaces. 
Boiler plate 38;*»s of an inch thick. 
Flame bed 5 inches from the boiler. 
There was no flue, but the flame-bed was carried up 
nearly to the water-mark. The draught was thereby re- 
duced to a thin and rapid current of 5 inches deep; under 
such circumstances the surface of the bottom of the boiler 
does not in any case coat with soot. 
Quantity of water evaporated from a temperature of 60°. 
lbs. 
When this boiler was worked at its ordinary speed, 
the average result from one pound of coal was, 
wita a fire kept’ anches; thick <2... 5.4ss0..-2-4s.: 5.60 
Ditto 7 WHCHES ERICK. 6.c0022s020 jbres Oto 
Ditto Winches thick: .777....tha- tesd ess 5,93 
When worked briskly, and apparently pushed with 
i MRC RIMEECS cin cc ss teacces] ¢o cats vemecnetne tat ay av bao 6.09 
When in a dirty condition within, from a slight 
scale of sulphate of lime about the thickness of 
a sixpence or less, but in other respects under 
ordinary circumstances with a 7-inch fire......... 5.50 
When made perfectly clean and keen internally by 
means of muriatic acid, with a 7-inch fire ... .. 6.45 
This unusual activity produced by the muriatic acid con- 
tinued only for a day or two. The boiler by that time, with 
the water used, became glazed or smoothed, and the keen- 
ness was destroyed. 
This boiler at its ordinary speed evaporated, in 12 con- 
tinuous working hours, 27,267 lbs. of water from the tem- 
perature of 60°, and when pushed 38,678 lbs. 
The evaporating power of this boiler may therefore be 
VOL. XV. E 
