NAVAL STOKE INDUSTRY. 151 



absolutely fresh wood in which the sapwood is guarded against loss of resinous contents by evap- 

 oration and otherwise. 



Of practical importance is the demonstration, furnished in these investigations, that the resin 

 of the heartwood has lost its fluidity, being probably infiltrated into the cell wall, and therefore 

 (lie tapping for turpentine does not involve the resin of the heartwood or produce any change in 

 the same. 



Concerning the conditions which encourage abundant resin production we are also in the 

 dark. Trees standing side by side, and apparently under the same conditions, show widely differ- 

 ent amounts of resin. In general it may be said that light and warmth are prime requisites for 

 abundant resinitication, hence this proceeds more rapidly in open groves than close plantations; 

 abundant nourishment and energetic activity of life seem also advantageous to resin production, 

 hence a strong, fresh, warm soil furnishes more resin than a thin and cold soil, trees with full 

 crown and branches more than tliin-foliaged and densely crowded trees with small crowns; warm 

 and dry summers produce a richer tlow than wet and cold ones. 



METHODS III WORKING TREES. 



The methods of working trees for turpentine differ with the different species, as also in differ- 

 ent countries According as the resinous contents are found mainly in the bark or in the sapwood 

 or in the heartwood, we may discern various methods. 



(t) Chipping: this method consists in making a scar or chip on the tree, which is annually 

 enlarged, and gathering the liquid turpentine at the lower end of the chip or scar in recess (box) 

 cut into the tree; or else, as in France, in vessels; or else by allowing the resin to dry and be 

 scraped, as is done with the Norway spruce. 



(2) Bore-holes are applied in the tapping of larch, where the turpentine is formed or collected 

 in the heart. 



(.'5) Opening the resin vesicles of the bark and gathering by hand is applied in the case of 

 the balsam. 



The yield of resin and turpentine depends upon various circumstances besides the species from 

 which it is gathered, namely: (I) The dimensions of the tree; the larger the tree, of course, cute fiit 

 jxiribux. the larger the yield; the yield of trees of small diameter, 7 to 10 inches, may be from one- 

 half to one-third of those of larger diameter. (2) The conditions of site; all elements which further 

 large development of the crown, mainly open and sunny position, south or east exposure, will 

 increase the yield. (3) The weather, and especially the temperature, during the time of gathering; 

 the most favorable weather is changing temperature and humidity; long continued heat and long- 

 continued cold rains depress the yield, especially a cold spring predicts a poor crop; the flow of 

 t urpentine increases from spring to fall. (4) The duration of the bleeding process; in the first two 

 or three years the yield is or ought to be smaller than in the following years. With the Austrian 

 (black) pine the maximum yield seems to be reached in the trees of smaller diameter between the 

 fourth and sixth years; in the trees with larger diameter, over 10 inches, between the seventh and 

 ninth. Trees of these species on proper sites can be utilized for thirty years, but working becomes 

 less profitable after six or eight years tor the smaller and ten or twelve years for the larger sizes; 

 the expense of working growing too costly, the foliage becoming thinner, and the yield smaller. 

 (."" The aptitude and care of the workmen, which tells in the manner of making and enlarging the 

 chips and of dipping and scraping. 



PRINCIPLES TO BE OBSERVED IN TURPENTINE ORCHARDS. 



The principles which should be observed in the chipping process, the one practiced on the 

 largest scale, especially on pines, are as follows: 



>s/:r in- iii/r of trees to be tapped. There is not sufficient experimental knowledge at hand to 

 determine the most advantageous size of trees for tapping, either as far as greatest annual pro- 

 duction of turpentine or safety to the life of the tree is concerned. The. experiments on Austrian 

 pine, recited further on, seem to show that trees above 10 inches in diameter yield much more 

 than smaller trees, almost double the amount of resin, with a higher percentage of spirits of 

 turpentine. It also stands to reason that the safety of the tree, where this is of moment, is better 



