196 Fuel Economy. (April, 
connected. This arrangement does away with all flange 
joints, so that no leaking can possibly occur, and also 
secures a perfectly smooth surface for the action of the | 
scraper, which revolves, ascending and descending according 
to the spiral form of the coil. It is said that a saving of at 
least one day’s consumption of fuel per week is effected. 
The water having a continuous circulation, all sediment is 
held in solution and passes through the coils, thereby 
avoiding deposit. Each coil is tested to a pressure of 300 lbs. 
per square inch before leaving the works. Economisers of 
various forms make a great show, and it is difficult to say 
which is the best. | 
Messrs. Twibill, of Manchester, exhibit a fine perpen- 
dicular economiser, which consists of a collection of tubes 
set vertically in the flue. These tubes are tested to a 
pressure of 500 lbs. to the square inch. Some experiments 
were performed some time since after the heater had been in 
use for some time. ‘The first test was taken at six o’clock 
on Monday morning; the temperature of the water in the 
pipes was 140° F. At four o’clock on the same day it had 
risen to 284° F., on Friday morning at six o’clock the 
temperature was 250 F., and at four o’clock the same day 
it had risen to 310° F.; and the average temperature of the 
water throughout the week was 273° F. An experiment was 
performed at Messrs. Romaine and Callender’s mill, and the 
average temperature of the water was 295 FI’. The scrapers 
are peculiar to Twibill’s machine; they meet round the 
tubes and have chisel edges, which, by a special arrange- 
ment, press against the tube, and actually cut off the soot 
and tarry matter which accumulates upon the pipes. 
Messrs. Green, of Wakefield, exhibit the finest vertical 
economiser; the joints of their economiser are all turned 
and bored socket-joints, ‘‘ metal and metal” forced together 
by powerful machinery expressly adapted for the purpose. 
Their economisers are in operation to 65,000 boilers, 
representing 2,500,000 horse-power. 
Nield’s improved fuel economiser is on the same principle 
as Andrew Bell’s. ‘This economiser is arranged in sections, 
each section consisting of a number of cast-iron ring-shaped 
pipes, through which the water is caused to circulate. The 
inlet and outlet passages of each ring are close together; 
and as this is the sole joint, and the only fixed point in the 
ring, itis quite impossible that the expansion and contraction 
of the ring can affect the joint in any way; this is a very 
important advantage, and is peculiar to this economiser. 
