MR. HAMERTON'S PAPER ON ARBORICULTURE. 



EXPLANATION OF THE PLATES. 



Having given a table of diameters, circumferences, and areas, advancing by ^th 

 of an inch in diameter, any one may be enabled to know how soon, by a certain 

 annual increase, a tree will double itself in quantity of wood, — as the area of 5 in. 

 diameter would be 19,6350, of 7 in. 38.4846, which area, multiplied by the length 

 of the stem, will give the solid contents. 



PLATE I. — A horizontal view of the growth of wood: some of the circular 

 spaces are shaded to assist the eye in distinguishing more readily one from 

 the other, and the more easily comprehending the dimensions ; circles being to 

 each other as the squares of their diameters. The tree must advance in the 

 respective proportions to enable it to double its previous bulk ; and it will be for 

 any one to ascertain how many years' growth of his trees will be required 

 to make up the requisite number of inches in diameter necessary to obtain double 

 wood : if the diameter be two-eighths of an inch on each side of the circle— four- 

 eighths in the whole diameter — then the tree would make the 2 inches required in 

 four years, — paying 25 per cent. On the other side 1 have given a vertical sec- 

 tion of the same : at the bottom of Plate I, 6, I have given a magnified specimen 

 of an oak, to show the cellular as distinguished from the fibrous tissue. The 

 cellular is the first wood grown in the year, and the weakest part of the wood ; in 

 quick grown wood the fibrous tissue is much larger and stronger, and it is proved 

 that the one will bend when the other will break. The answer given by Mr. 

 Andrew Knight to the question of Lord Glenbervie, viz., whether oaks which grew 

 in poor soil and slow, were of a firmer nature and more durable timber than when 

 grown in a richer soil? was — " No. Their timber is more porous, lighter, and less 

 durable ; a layer of very porous wood marks the commencement of each year's 

 growth, and when the growth is small these porous layers almost touch each other," 

 (as in the specimen I have given of oak marked c, Plate III. J The experiments 

 of Professor Barlow, at Woolwich, prove the same. Two specimens of oak were 

 selected, one from a fast grown tree and the other from one slow grown : two 

 pieces were squared down to 2 in., and were broke on props 50 in. asunder ; the 

 one from the quick grown specimen deflected l-50th of its length, with 660 lbs., 

 and was broken with 999 lbs. ; the other, the slow grown, deflected l-50th of its 

 length with 414 lbs., and was broken with 667 lbs. 



PL A TE II. — I have given a tree to show some branches I think proper to cut 

 off. The two branches marked a a, which rival the leader, I would only shorten, 

 leaving two small shoots to keep alive the branch. At b there is no other mode 

 to be adopted but that of removing fhis branch by a close cut. At 6 is given an 

 example of a branch having been cut off many years before, and no union having 

 taken place internally with the new and the old wood, the fact, however, being 

 concealed by the bark outside ; when such a tree is cut down, the old and the new 

 separate immediately. I have a great many specimens to prove this. On the 

 back of this Plate, 1 have given four plants, two as first planted, 2 feet high and 

 4 feet apart, which are the usual proportions. The two tall trees at the same dis- 

 tance, neglected for perhaps fifteen or twenty years, and from 20 to 30 feet high : 

 if the distance of 4 feet was proper at first, it cannot be so always. 



