566 Readixg-Coursk for Farmers. 



because of less expenditure required for maintenance. (Jn the othef 

 hand, there may come a point in the cost of construction when the inter- 

 est on the increased investment will more than pay fur maintenance. 



Stone has long been used for basement work and when available is in 

 many respects the best for such purpose. ( )bjection is often found to 

 basement walls because of the condensation of moisture on them. This is 

 because the inner surface is cooled by conduction and because the stone 

 is a good conductor of heat. The room within stone walls is less likely, 

 however, to be cooled by an actual change of air than in the ordinary 

 wooden construction, particularly wdien it is warm above ground so that 

 the room contains relatively warm moist air with relatively cold surface 

 walls. This condensation of moisture on the walls is not in itself harm- 

 ful but rather beneficial as abstracting moisture from the air. Moist 

 walls, however, are a symptom or indication of an improper condition of 

 the air of the room. No benefit is secured by changing the character of 

 the wall unless the character of the contained air is thereby changed. 



In the building of the superstructure, wood is still the chief material 

 used, although a barn has recently been constructed in tliis State whose 

 frame work is of steel. (Fig. 337.) 



\\'hen timber and labor were cheap, barns were built with heavy 

 frames, dependence being placed on the direct support of the post. Such 

 l)arns are thoroughly strong and rigid, but are now found expensive on 

 account of the -price of lumber and labor, and on account of the posts the 

 space cannot always be so conveniently or economical!}- arranged. This 

 has led to the construction of so-called plank barns. 



Two principles have been taken advantage of in the construction of 

 l)lank l)arns : 



( I ) That the carrying strength of two beams are not directly pro- 

 ])ortional to their width but are proportional to the square of their depths. 

 The carrying strength of a 4 x 4 is to a 2 x 8 as 20 is to 66. Great addi- 

 tional carrying strength for the amount of material used is therefore 

 secured by using plank on edge rather than square timber. It will be ob- 

 served, however, that the lateral strength of the material is lessened, and 

 therefore not so able to withstand any lateral tlnmsts as when square tim- 

 bers are used. For this reason plank barns, in the construction of which 

 this fact has been overlooked, have been known to sufl'cr from wind 

 ])ressurc and sometimes from the interior jiressure of hay or other forage. 



(2) In the cfinstruction of plank barns greater use has been made 

 of the truss than in older barns, in doing away with interior posts and in 

 securing strength elsewhere. The ])rinciple on which the truss is based 

 may l)c illustrated by stating that if the ends of three lath are united 

 into a triangle by the use of a single nail at each angle, the structure will 



