OF ARTS AND SCIENCES. 



805 



heat that It would be impossible to tell whether the deflections were 

 caused entirely by the load, or partly by the heat of the room ; hence 

 it was thought best in making these experiments to use kiln-dried 

 timber. 



The small beams upon which the experiments were made were 

 taken from two spruce planks, selected from lumber which had been 

 cut in Maine during the previous season. The planks were kept in a 

 drying-kiln three weeks, and were then cut up into pieces about two 

 inches square and allowed to dry until tested. For convenience the 

 beams cut from one plank are classed as Series No. 2, and those from 

 the other as Series No. 3 ; Series No. 1 including those beams pre- 

 viously experimented upon, which were discussed in my previous 

 paper. 



All the pieces of wood experimented upon were what might 

 almost be called perfect pieces, being straight grained and free from 

 knots. They were about Ih inches square, and 40 inches between 

 the supports. The exact dimensions, with other data, are shown in 

 the tables. 



TABLE I. 

 Sekies No. 1. Unseasoned Spruce. 



Tables I., II., and III. are so arranged that a comparison of the 

 strength and stiffness, together with the ultimate deflection of the 

 pieces in the different series, can easily be made. 



VOL. XVII. (n. S. IX.) 20 



