592 TRANSACTIONS OF THE 



Crystal Palace is built of iron and glass, each of single thick- 

 ness, without other lining or covering to the walls. In the 

 SQuthern offices in that building, occupied by the clerks of this 

 Institute at its late exhibition, the heat became almost intolera- 

 ble so soon as the sun shone upon that part of the building, 

 though late in November, but when the sun iiad set, or a shadow 

 fell upon the wall, the temperature instantly fell and in a very 

 short time was the same as that out of doors. 



In the first case, the dark walls readily absorb the heat from 

 the sun's rays, but being poor conductors are exceedingly slow in 

 transmitting it to their internal substance, or in showing any rise 

 of temperature upon their inner surfaces. When these warm 

 beams are withdrawn, these massive blocks are equally slow in 

 imparting to the outer air, the heat they have been so long in 

 acquiring, or which has been contributed to them from the inte- 

 rior apartments. They become, in fact, great reservou'S of caloric, 

 slow both in filling and exhausting. 



In the other case^ the iron portion of walls is an equally ready 

 recipient of solar heat, but being thin, and moreover a good con- 

 ductor, soon becomes throughout its substance of a higher tem- 

 perature than the air of the room within, and at once begins to 

 impart to it of its own heat. In the same manner, the floor and 

 all other opaque substances, upon which the smishine from the 

 windows may fall, become, in turn, absorbents and radiators, and 

 the air which was more unaffected by tiie direct solar rays, when 

 they passed through it, readily absorbs the heat from the hot sub- 

 stances with which it is in contact, and rising, gives placet© other, 

 until the whole is much warmer than the open air circulating 

 outside; now remove the heating cause, and the current begins 

 to set in the other direction through the same channels. The 

 walls, in turn, give up their heat to the external wdnds, and 

 absorb it from the internal air, which continued to derive it from 

 any substance warmer than itself, till all are again reduced to 

 the same temperature. Here we have in one day, the phenomena 

 of both winter and summer. 



It will be seen that in either Qf these cases the air of the inte- 

 rior is heated or cooled only by contact with the walls or other 

 substances, themselves heated or cooled from the outside. The 

 remedy for these effects then is evidently to form the walls in 

 such a way that they shall not transmit caloric from one surface 

 to the other. To accomplish this, a thick and solid stone wall 

 has often been resorted to at enormous expense and with much 



