Book II. 



VALUING PLANTATIONS. 



663 



girth, by nine feet in length, will be found to contain one solid foot of wood, and will produce thirteen 

 pounds and a half of bark." {Forester's Guide, 170.) 



4073. When growing trees are valued, an allowance is made from their cubic contents 

 for the bark. The rule given by Monteith is, " When the girth or circumference is any 

 thine from twelve inches up to twenty-four inches, then deduct two inches ; from 

 twenty-four to thirty-six, three inches ; from thirty-six to forty-eight, four inches ; from 

 forty-eight to seventy-two, five inches; and above seventy-two, six inches. These 

 deductions," he says, " will be found to answer in almost all trees ; unless in such as 

 are very old, and have rough and corky barks, or barks covered with moss, when an 

 extra allowance is to be made." i Forester's Guide, 180.) 



4074. Tn valuing measurable oak-trees, many persons proceed on the data that every 

 cubic foot of timber will produce a stone (sixteen pounds) of bark. " This," Monteith 

 says, " is not always correct ;" and he states the following facts from his own expe- 

 rience, with a view to assist beginners in ascertaining the quantity of bark from different 

 trees. " An oak-tree, about forty years old, measured down to four inches and a half as 

 the side of the square, and weighing only the bark peeled off the timber that is measured, 

 without including the bark of the spray, &c, every foot of measured timber will 

 produce from nine to eleven pounds of bark. An oak-tree of eighty years old, weighing 

 only the bark peeled off the measurable timber, as above, every foot will produce from 

 ten to thirteen pounds of bark. Every foot of large birch timber, peeled as above, will 

 produce fourteen pounds of bark. Every foot of mountain-ash, as above, will produce 

 eleven pounds and a half of bark. Every foot of the willow, unless a very old one, 

 will produce from nine to eleven pounds of bark. Every foot of larch fir, not exceeding 

 thirty years old, will produce from seven to nine pounds of bark. The bark of trees, 

 particularly the oak, is peeled off, every branch and shoot, down as small as an inch in 

 circumference." {Foresters Guide, 189.) 



4075. To facilitate the measuring of standing timber, various ingenious instruments and machines have 

 been invented, by Monteith, Gorrie, Rogers, and others. Perhaps the most generally useful is Broad's 

 callipers (Jig. 599). This instrument is composed of two thin pieces of deal about thirteen feet long, with 



a brass limb or index (a), on which are engraven figures denoting the quarter girth in feet and inches. 

 Raising the instrument, the index end (a) is taken hold of, and the other applied to that part of the trunk 

 where the girth is to be taken, opening it so wide as just to touch at the same time both sides of it, keeping 

 the graduated index uppermost, on which the quarter girth will be shown, allowing one inch in thirteen 



gQO for the bark. For taking the height of 



a tree, rods of deal or bamboo, seven 

 feet long, made so as to fit into ferules 

 at the end of each other, tapering as in 

 a fishing-rod, may be used. Fiveof them 

 with feet marked on them would enable 

 a man quickly to measure the height of 

 a trunk of more than forty feet as he 

 would reach above seven feet. Mon- 

 teith's machine being described in the 

 Em-i/clu/KTdia of Gardening (2d edit. 

 5 6970), and Gorrie's in the Gard. Mag. 

 (voL ii. p. 9.), we shall here confine our- 

 selves to the invention of Mr. Rogers. 



4076. Rogers's dendrometer (Jig. 600) 

 consists of a tripod stand, and a machine 

 for taking angles horizontally as well as 

 vertically. An upright stem arises from 

 the top plate, at the end of which is a 

 ball, with a hole perforated through it, to 

 receive the horizontal stem of the in- 

 strument ; b c may be called the base 

 limb of the instrument, which is to be 

 placed in a truly horizontal position, 

 and adjusted by the suspended level (rf). 

 The limb (e) rises on a joint at r, and 

 slides upon a vertical arch (J) which is 

 graduated. At the joint (c) there is an 

 eye-piece, through which the surveyor 

 looks along the side of the bar (6) to a 

 small point, or rising edge, at the end of 

 the bar ; the part of the tree cut by this 

 line of observation will, if the instru- 

 ment is properly adjusted, be perfectly 

 horizontal with the eye-piece. An ej e- 

 piece is also placed at c, on the upper 



