SCIENTIFC NEWS. 317 



4. The proportion of steam pipe required to heat a given 

 space. 3^ The substance and colour of steampipes. 4. 

 Their direction and arrangement, 5. The modes of con- 

 necting them. 



1. A cubic foot of boiler will heat about 2000 cubic feet Size of boilera 



• 11 1 1 • • ^"" quantatf 



of space m a cotton mill, where the temperature is iii ge- of fuel. 



neral from 70° to 80° of Fahrenheit. The boiler is supposed 

 to be of the shape commonly used for a steam engine, and 

 25 cubic feet to be equal to a horse's power. Where the 

 boiler is separate, and not u^sed for the joint purpose of 

 working an engine and warming a building, it should be 

 considerably larger than in this proportion, to avoid the in- 

 equality of heat incident to a boiler working at its full capa- 

 city : 25 cubic feet of boiler require about 14lbs. of good 

 Newcastle coal per hour. 



2. Every square foot of exterior surface of steampipe Pioportiou of 



. , * pipe to space. 



will warm about 200 cubic feet oi space in a cotton mill. A 



small chapel has been warmed comfortably with half that 



proportion. The safety valve in the boiler is supposed to 



be loaded about 2|- lbs. to the square inch. If the steam 



were stronger, it would give more heat, but it would be 



difficult to keep the joints of the pipe steam tight, 



3. Cast iron pipes give out above twice as much heat as Materials ©f 

 copper, or tin, unless the tin be painted black. When the P^^^^* 

 surfaces are equally dark, and equally rough, there is no 

 apparent difference. The thicker the pipe the more uniform 



the temperature ; but on account of the expense they are 

 generally not more than | or | of an inch thick. 



4. The expansion of cast iron pipes may be estimated at Their arwnge- 

 y\t of an inch for every 10 feet in length. Vertical pipes, 

 being equally heated all round, continue straight ; but hori- 

 zoatal pipes bend, because the upper side is heated mostj 

 and this endangers the joints. Vertical pipes too may be 

 used as pillars for supporting the floors. In the arrange- 

 ment of the pipes two points require considerable attention. 

 First, conveniently to expel the air; and, secondly, to take 

 off the water proceeding from the condensation of the steam. 

 When the steam enters the pipes, it acts as a piston, driving 

 the air before it. This principle should be kept in view in 

 fixing on the place of the opening for the escape of the air. 



After 



ment. 



