Chemical and Physical Papers. 55 



measure across the square from 12 on the blade to 9 on the tongue 

 you will find 15 on the rule. Take 12 on the tongue and 15 on the 

 blade, make the cutting mark on the purlin on the 12-inch edge, 

 lay the timber on its side, and take 9x15 on the square, lay on, and 

 mark across on the 9-inch edge, and the miter will be marked com- 

 plete. So it will be seen that the figures which govern the pitch 

 of the common rafters must be kept in mind all through. 



A little practice with the problems above set forth will make the 

 beginner familiar with the methods and enable him to comprehend 

 the principles. The above will work out any problem of cuts in 

 the framing of an ordinary roof. For the more complicated prob- 

 lems, such as cuts for irregular hip roofs, bevels of hoppers, cut- 

 ting spring moldings, etc., a deeper study into the principles of 

 the square is necessary. 



