

Chemical Papers. 63 



The disintegration of the wall of this room may be accounted for 

 by considering that the cold air, as it is warmed by its passage over 

 the steam-pipes, quickly acquires a greater capacity for taking up 

 moisture, and so it abstracts moisture from the nearest available 

 source, namely, the plaster of the walls ; this plaster having lost the 

 water that is necessary to form the crystals of gypsum, falls to pieces 

 just as it would before the blowpipe. 



It is a well-known fact that the lime-plastered wall will fall to 

 pieces if kept very damp for considerable time, and this is also true 

 of walls made of cement plaster. There is no record, however, of hot, 

 dry winds tending in any way to injure walls of this material, and 

 it is probable that only under the special conditions mentioned 

 above this disintegration could take place. 



