66 TIMBER AND TIMBER TREES. [cuap.x. 
Fir of the same dimensions, as shown in subsequent 
Tables, might be loaded to 67 tons. 
As before stated, I have applied this description of 
test to a great variety of woods, and it has enabled me 
to ascertain with tolerable accuracy the amount of strain 
they will each bear to the square inch of base. The 
general result of the trials with gradation of lengths 
confirms, in some degree, the theory of a four-fifths pro- 
portion of base to length, and shows it to be at least 
approximately correct. Therefore, with this data for 
our guidance, aided by a little practical judgment, there 
should be no difficulty in determining the scantlings of 
props and supports for all ordinary purposes. 
There is yet another description of test to be noticed, 
namely, that for ascertaining the elongation of the fibres 
under certain strains. The experiment was made in one 
of the royal dockyards upon two pieces of English 
Oak, each 2x 2 x 48 inches, and very carefully con- 
ducted—note being taken of the elongation in a length 
of 3 feet; the mean results were found to be as follows, 
viz. -— 
TABLE XXIII. 
With the weight of} 2 3 4 5 6 7 tons, 
The elongation was | ‘oO |'03125]°04617|‘07812| ‘1250 |'15625] ins, 
With the weight of | 8 9 10 11 12 -. | tons, 
The elongation was |*19375 |*23437} ‘2500 “2500 | “3125 | w. | ins, 
