484 On the Construction of Kitchen 



ders or into the reservoir which feeds them. In doing 

 this, care must be taken to cause the steam to descend 

 perpendicularly, from the height of eight or ten feet, 

 before it enters the water where it is intended that it 

 should be condensed ; and the end of the tube through 

 which the steam descends and enters the water should 

 be plunged to a certain depth below the surface of the 

 water. 



I shall finish this chapter and conclude this Essay by 

 giving a short description of two very simple contriv- 

 ances, which have been put in practice at the house of 

 the Royal Institution, and which have been found to be 

 very useful. The one is a contrivance for preventing 

 most effectually the bad effects of the alternate expan- 

 sion and contraction by heat and cold of the metallic 

 tubes which are used in conveying steam to a consider- 

 able distance ; and the other is a substitute for safety- 

 valves in an apparatus for heating rooms by means of 

 steam. 



Of the Means that may be used for preventing metallic 

 Steam-tubes, of considerable Length, from being in- 

 jured by the alternate Expansion and Contraction of 

 the Metal by the different Degrees of Heat and Cold 

 to which those Tubes are occasionally exposed. 



We will suppose the tube in question to be of copper, 

 and eight inches in diameter (which is the size of that 

 used for warming the great lecture-room at the Royal 

 Institution). Let this tube be made in lengths of ten 

 feet; and instead of joining the ends of these tubes 

 together immediately, to form one long tube, let a very 

 short tube or cylinder, of only one or two inches in 

 length and 24 inches in diameter, closed at each end 



