HEATING BY HOT WATER. 187 
extant. They also heat very quickly, and if properly 
set and worked are by no means extravagant in fuel—this 
may at least be truly said of the newer and improved forms, 
such as the Champion, made by the Thames Bank Iron 
Co. (see Fig. 127), though some of those first constructed 
undoubtedly consumed a large amount of fuel in proportion 
to the amount of work done. 
These boilers being entirely constructed in sections, and 
the tubes being easily removable, have also considerable 
advantages, as a cracked or faulty tube can be taken out 
and replaced in a very short 
time. This class of boiler can 
also be set in comparatively 
shallow stoke-holes, and one 
form with only a single row of 
pipes over the furnace, though 
scarcely as economical in work- 
ing as those in which the 
draught is taken forward and 
backward again. A very great 
improvement in the heating 
power and general efficiency of 
this type of boiler has been 
effected by casting the pipes with a web or feather 
on each. This, when the pipes are fixed as shown, 
prevents the heated air, etc, from passing too 
directly into the chimney, and forces it to travel the 
whole length of the boiler and back twice or thrice, when 
it will have parted with the greater part of its caloric. 
Where, however, special or important work, such as 
forcing, etc., is carried on it is always advisable to set 
Fig, 128. 
