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arboretum and fruticetum.

PART 111.

not to collect resin more than five or six times from each tree. 3dly, Not toscrape off the resin before the month of July or August of the year after thatin which the groove has been made, or its edges fresh-pared, in order to givethe resin time to harden, and the bark under it to heal sufficiently to preventthe rain from rotting the wood; and, 4thly, Not to make more than one grooveat a time upon a tree if it be small, or two if it be large; and never tomake the grooves more than 4 ft. in length or, more than 1 in. or I Jin.in width. Attempts have been made to show that resin may be procuredfrom trees artificially, without seriously injuring them ; and one author (M.Burgsdorf) asserts that, if the spruce fir has attained its full growth, all itsresin may be extracted from it without injuring the quality of the wood forfuel or charcoal; while another (M. Malus) assures us that the timber of thetree may still be used even for the purposes of construction. Du Hamel,Hartig, and most other authors, however, are of a very different opinion;Hartig having found that carrying the process of extracting the resin to anextreme degree, not only renders the wood unfit for the purposes of con-struction, but even makes it almost useless for fuel. In Sweden, and on thesouthern shores of the Baltic, a similar opinion prevails j and the resin isthere only collected from those trees which have been pruned; in whichcase it generally oozes out from the wound.

Mode of preparing the Burgundy Pitch. This pitch, or rather resin, isprincipally made in the Vosges. The slightest scar in the bark of the treewill be sufficient to make the resin ooze out; but it must be observed that itnever flows to the ground like turpentine, but congeals as soon as it issuesfrom the wound, and remains attached to the bark in tears or crystals,something like the gum of cherry trees. To procure the sap in abundance, itis necessary, as we have already observed, to take off a narrow strip of bark,which is done with the broad end of the instrument before mentioned, orwith a small hatchet; great care being taken not to wound the wood. Theresin from young trees is softer than that from old ones; but it is alwaysdry enough to be put into bags, in which it is kept till a sufficient quantityis collected. To prepare the pitch, it is first necessary to melt the resin ;and, for this purpose, caldrons are set in masonry, in such a manner thatthe fire only touches the bottom of the caldron; and the chimney iscarried to such a height, or to such a distance, as to prevent all dangerof the flame issuing from it being driven by the wind or other causes on theresin. A quantity of water is then put into the caldron so as to fill it4 in. or 5 in. high; and into this the resin is put a little at a time, till thecaldron is about four fifths full. A gentle fire is then lighted below,which is gradually augmented, till the water boils, and the resin is all melted.It must now be gently stirred; after which, the fire is withdrawn, and theresin is in a state for being purified. This is done by pouring the liquidfrom the caldron into a bag made of coarse linen, which has been previouslywetted ; filling it not more than two thirds, and afterwards putting it undera light press. The resin flows pure and clear into small casks made offir wood; and in this state it is the yellow Burgundy pitch of commerce.The refuse left in the sack, being pressed a second time, yields a blackerresin, which is used for the same purposes as the colophony of the pine;and what remains, after this has been pressed out, is burned in order tomake lampblack. In general, 1001b. of resin, as collected from the tree,yields 50 lb. of Burgundy pitch, and 2 lb. of colophony. Trees grown onfertile soils are said to yield a greater proportion of resin than those grownon poor soils; and the pitch is said to be better when the resin has beencollected in a hot dry summer, than in a cold and humid one. An essentialoil is produced from the Burgundy pitch, by distillation ; but it is very inferiorto spirit of turpentine. A strong and vigorous spruce fir will yield, everysecond year, from 40 lb. to 50 lb. of congealed resin; and this may be col-lected for from 20 to 25 years, if no other value is set on the tree; but, if thecollection of the sap be continued for this length of time, the tree becomes