PLANTING. 77 



and that in all plantations where the pruning and thinning- have not been 

 judiciously executed, the trees which stand on the outside of the plantation, 

 or on the sides of the drives, are larger, say double the size, or have been 

 of much quicker growth than those in the interior of the plantation. Now 

 the greatest comparative degree of strength and hardness of the woods of 

 the two trees is proved to be in that of the larger, or the tree whose growth 

 was most rapid and \igorous the sap wood being of course larger in 

 the fast-growing tree, as are all the annual layers of the heart wood. If the 

 reader will look back to page 8, where the structure of the wood of different 

 species of trees is described and figured, it will be seen that the wood of 

 the oak, a comparatively slow-growing tree, is distinguished from the wood 

 of the poplar, a fast-growing tree, by having the cellular structure compa- 

 ratively confined to the concentric circles which mark the annual increase 

 of wood ; that the number of cells between these concentric circles are 

 few, though of a larger diameter, while in the wood of the poplar they are 

 dispersed in great number, or crowd the whole surface of a section of the 

 wood. If the hard wood of the locust (Jig. ?/, p. 10) be compared to the soft 

 wood of the fir (Jig. o), to the laburnum (fig. <?), the lime (jfig.p>\). 11), 

 sweet chestnut (Jig. e), to the horse-chestnut (Jig. 7i), and every hard and 

 durable wood to the soft and non-lasting kinds, the same clear and marked 

 distinction will be evident, i. e. the hard, tough, and durable woods have 

 the cells chiefly confined to the annual rings, or thinly scattered in irregular 

 groups, leaving comparatively wide intervals of apparently solid fibre, while 

 all the soft or non-lasting woods have the entire substance pervaded with 

 minuter cells, in number and regularity that may be compared to the texture 

 of fine lace or net work. 



These then are the external discriminating characters of hard and of 

 soft woods ; and let us now apply these to distinguish the woods of fast 

 and of slow growing trees of the same species, and we find that the 

 wood of the fast-growing tree has wider intervals between the concentric 

 circles, or congeries of cells, or, in a word, fewer cells to the size or diameter 

 of the wood, and is consequently wood of greater strength, toughness, and 

 durability. The experiments of Professor Barlow on the strength of dif- 

 ferent woods confirm the above conclusions*. The opinion of Thomas 



* Mr. Withers, in his Letter to Sir H. Stewart, p. 115, states, that he received from Mr. 

 Boorne, of Erpingham, a respectable timber-merchant, two specimens of oak, one taken from 

 a fast, and the other from a slow growing tree. No. 1. was grown upon a very strong good 

 soil, the age of the tree about sixty years, and it contained from thirty-eight to forty feet 

 of timber. No. 2 was about one hundred and twenty years old, and was grown upon a 

 light soil, with gravel about two feet below the surface. These specimens being submitted 

 to Professor Barlow, of the Royal Academy, Woolwich, were tried, and gave the^ follow 

 ing results : 



No. 1, 



Deflected one-fiftieth of Comparative 



Specific gravity. its length with Broken with strength. 



903 GGOlbs. 9991bs. 1561. 



No. 2. 

 856 4141bs. 6771bs. 10581bs. 



No. 1, it appears, is, therefore, of about medium strength, my mean number being for 

 English oak, 1470. 



No. 2 is very weak, my weakest specimen being 1205. (See Essay on Strength of 

 Timber.) 



Mr. S. Farrow, timber-merchant, Diss, Norfolk, states to Mr. Withers, that ' It has 

 always been a custom with me when I wanted a mild, tender piece of oak for any purpose, 

 to look out for a slow-growing tree to cut it out of; and, on the contrary, when hard wood 

 was wanted, to take the fast-growing tree, one which, before being felled, was in full and 

 rapid growth, and I have ever found the latter much the most durable wood.' Two speci- 

 mens of oak communicated by Mr. Farrow, No. I, of a tree reared close to the rick-yard of 

 the farm, and by the side of a ditch into which ran a great deal of moisture from the yard, 



