x.] BRITISH OAK. 65 



quired to crush them was, severally, 7,640 Ibs., 7,224 Ibs,, 

 and 7,058 Ibs., per square inch of base, which, if com- 

 pared with 7,978 Ibs. on the one-inch cube of the same 

 seasoned wood, shows an apparent diminution of strength 

 in each of the next larger sizes ; the average force 

 required to crush the complete parcel of four sets of 

 cubes being 7,475 Ibs. The average strength of the 

 unseasoned pieces of the same dimensions only 4,9 15 Ibs. 

 to the square inch of base. 



In the experiments (Table XVII.) on a set of fifteen 

 specimens, each 2X2 inches, and severally varying only 

 I inch in length from I to 12 inches, and then by 6 

 inches, until a length of 30 inches was obtained, it was 

 found that the piece 5 inches in length bore the maxi- 

 mum pressure of 8,820 Ibs., or 3 '937 tons on the square 

 inch, the resisting power of each of the others being less, 

 while the piece of 24 inches was crushed by about two- 

 thirds the strain of that of 5 inches in length. 



From this it would appear that the proper proportion 

 of sectional area to length for this description of timber 

 is as about 4 : 5 ; or, in other words, the superficial area of 

 the base in inches should not be less than four-fifths 

 the length of the pillar or column in inches. 



Thus, if it were required to ascertain the scantling 

 for an Oak pillar, 144 inches in length, to ensure its 

 carrying the maximum of strain, we should have 

 v/ ^ 10 73 inches for the side of that pillar, and 

 according to the ascertained strength of our specimen, 

 5 inches in length, this would be capable of bearing a 

 weight of 453 tons. Even if we observe the rule, recom- 

 mended by many authorities, of only loading to one- 

 fourth of the calculated strength, we may still consider 

 it equal to the strain of 113 tons, while a pillar of Riga 



F 



