200 GREENHOUSE CONSTRUCTION AND HEATING, 
a working man, or one whose means are limited, but a 
few shillings can often be spared where even the same 
number of sovereigns would be out of the question. To 
all owners of small green- or plant-houses of any kind 
who desire to heat them efficiently and yet find the cost 
of a proper ready-made apparatus, whether consuming 
coke, gas, or oil, beyond their means, I can strongly 
recommend the double-flue described on p. 205, and 
even if anything beyond this is required, it is easy to add 
a row or two of H. W. piping and heat it from the same 
fire, as there shown. A coil boiler (already described 
and illustrated), in connection with a few yards of piping 
of some kind, will, if properly arranged, afford even more 
satisfactory results, at a much lower cost than the ordinary 
run of hot-water apparatus, and something of this kind, 
in connection with a flue, will usually afford the highest 
possible degree of efficiency, combined with a very small 
consumption of fuel. 
Hot-Water Apparatus to Consume Gas or 
Oil.—The more or less varied forms of these are now 
somewhat numerous, but really useful and effective makes, 
with a reasonably low consumption of fuel in comparison 
with the work done, are few. The construction of the 
boiler is the most important point, the arrangement of the 
piping being a comparatively simple matter. As previously 
stated, all the apparatus included in this section are only 
suitable for houses of comparatively small size, almost 
any type of boiler burning coke or coal (anthracite) being 
decidedly more economical where lengths of piping of 
over about 100ft. have to be heated. 
The old conical-shaped boiler for gas, shown in Fig. 188, 
