The results in the first row of the second column were in each case a mean from about three experiments upon cylinders of wood, turned to be 1 inch diameter, and 2 inches long, flat at the ends. The wood was moderately dry, being such as is employed in making models for castings. The second row of figures gives the mean strength as before from similar specimens, after being turned and kept drying in a warm place two months longer. The lengths of the latter specimens were, in some instances, only 1 inch, which reduction would increase the strength a little. But the great difference frequently seen in the strength as given by the two rows of figures, shows strongly the effect of drying upon wood, and the great weakness of wet timber, it not having half the strength of dry.

Hodgkinson has shown the strength of short columns of the same material to be directly as the area of section.† This seems easy to conceive, as bodies of the same nature always become crushed by sliding off in an angle, which is nearly constant; the height of the wedge, which would slide, being in timber usually about half the diameter or thickness of the specimen.

* 'Phil. Transactions,' 1840.

† ' Trans, of Brit. Association,' vol. vi.

144. Table XXII. - Of The Resistance To Crushing In The Direction Of The Fibres Of Short Pillars Of Different Kinds Of Wood, Chiefly Grown In America; And Of Common Use In That Country For The Purpose Of Construction. (Hatfield.*)

The pieces of wood used in the experiments from which the above Table was compiled were of ordinary good quality, such as would be deemed proper to be used in framing. They were 2 inches long, and from 1 inch to 1 1/2 inch square;'some were thicker one way than the other. There were generally three specimens of each kind.

145. Hodgkinson has proved experimentally of rectangular pillars of timber, that of the greatest strength, where the length and quantity of material is the same, is the square.†

* ' American House Carpenter.

† ' Experimental Researches,' p. 351.