BIED HOUSES AND HOW TO BUILD THEM. 



13 



FIG. 35. Longitudinal vertical section of 

 martin house; lowered, and doors closed. 



FIG. 36. Roof of martin house 

 attached solidly to pole. 



FlG. 37. Martin 

 house lowered; 

 doors closed. 



FIG. 38. Martin 

 house in place; 

 doors open. 



FIG. 39. Proper way to 

 make first "hitch" of 

 rope on hook of coun- 

 terweight. 



