To heat a glass house, size about 10 ft. square, for growing early cucumbers, a boiler to burn coke, with 3-in. or 4-in. cast-iron hot-water pipes, is recommended. A gas boiler would not prove so economical and requires careful fixing to shelter it from the wind and weather, which may cause it to light back or be extinguished. The Loughborough type of boiler, which is supplied with pipes, etc., complete, is generally found to be suitable. The pipes have expansion joints, and the whole is expressly made for amateurs' requirements, no skill being needed in putting up the apparatus. The boiler is fixed in the thickness or the wall and requires no pit or special provision of this kind. If the height of the house averages 7 ft., then 35 ft. of 4-in., or45 ft. of 3-in., pipe will be required. The pipe can be carried along two or three sides, below the glass, where the house is expected to be coldest.