128 
VEGETABLE GARDENING 
mercial houses is often much greater. As plants do not 
do well next to the walls, it is desirable to have walks 
there, and the house space can then be divided in such 
a manner as may seem convenient for the care and har- 
vesting of the crops to be grown. 
184. Steam versus hot water heating. — Hot water is 
unquestionably the best system for heating small houses, 
and there are many arguments in its favor for large 
ranges of houses. If pumps or a pressure system are used 
to secure rapid circulation, the radiating surface need not 
be much greater than in a steam system. The higher 
cost of installation has always been one of the greatest 
objections to hot water. With the pressure system in- 
stead of the open tank, the water is heated to a highei 
temperature and also made to circulate more rapidly. 
The advantages of hot water over steam may be stated 
as follows: (1) As the hot water in the pipes retains 
heat for a greater length of time, the boiler may be left for 
a iong'er time without attention. This is a great advantage 
in small greenhouses, where it would not pay to employ a 
night fireman. (2) Less fuel is consumed. (3) Proper 
conditions of moisture are maintained with less difficulty. 
Other advantages are often stated, but the foregoing are 
the most important. It is not so expensive, however, to 
install a steam plant nor so troublesome to make repairs. 
185. Pipes and piping. — Formerly, 4-inch cast iron pipe 
was used extensively and rust joints were in common 
use. Wrought iron pipe is now generally employed, and 
it is always threaded — an advantage that makes installa- 
tion more rapid and provides joints which are not so 
likely to leak. Most frequently 1 ]A and 2-inch pipe is 
used for the coils in hot water heating and ij4-inch pipe 
for steam heating, connecting with mains of proper size. 
Whatever the system, the pipe should be placed with the 
greatest care, observing the principles of the method of 
heating to be used. 
