LLv 10, lais 



HARDWOOD RECORD 



the American product. The sijecilio i^iruvity of tlio dry wood aver- 

 ages very closely to .500. Tests on the mechanical properties of 

 the wood from Grand Bassam show only slight variations, both 

 above and below, from the results from British Honduras mahogany 

 of the same weight. Accordiujjly we lind it being used in the 

 manufacture of combat propellers as extensively as the supply, 

 limited by transportation facilities, will permit. 



The mahoganies have various characteristics which adapt them 

 to propeller manufacture. One is the ease with which the wood can 

 be worked with tools, as mahogany has always enjoyed the highest 

 reputation as a cabinet wood. It is also comparatively inert to 

 changes in atmospheric conditions, and once dried and shaped will 

 warp, shrink and "work" less than almost any other wood, though 

 of course it falls short of being perfect in this regard. Again it 

 has no distinct linos ofi cleavage and can sustain local injury, such 

 as being pierced by bullets, with reduced tendency to split up or 

 shatter. , Still another feature is that the shrinkage in both the 

 radial and tangential planes is approximately the same, while in 

 many of our woods the tangential shrinkage is about twice as great 

 as the radial, thereby setting up severe internal stresses with every 

 change in the moisture content. 



In using African and American mahoganies for propellers it is 

 desirable to keep from mixing the species in the laminations, sim- 

 ply as a measure of precaution. The question of distinguishing the 

 two grades is therefore of importance and is giving some of the 

 manufacturers and inspectors trouble. The feature which seems to 

 be the most reliable for separating these woods is the presence in 

 Swietcnia of narrow white layers (sometimes reddish) which appear 

 on the ends like growth rings, while in the Kliaiia there are no 

 such lines of w^ood-parenchyma, although growth rings may appear 

 more or less distinctly. Sometimes these light colored rings are 

 evenly spaced from one-eighth to one-half inch or even more apart 

 and again they ma\' be very close in places and more or less irregu- 

 lar and wavy. Once this feature is recognized the woods can be 

 spotted instantly without the aid of a hand lens, if the ends are 

 fairly smooth. Another thing is the presence on some specimens 

 of American mahogany of "ripple-marks" or fine cross lines like 

 the teeth of a flat file. These are often quite distinct to the naked 

 eye on the smooth tangential or flat-sawn surface, and so far as 

 the writer knows are not found in the African mahogany or in 

 Spanish cedar. The absence of these lines does not signify any- 

 thing, but their presence can readily be made use of by anyone. 

 When the wTiter pointed out these cross lines to an old cabinet 

 maker he said: "Well, I have been working with mahogany on and 

 off all my life, but this is the first time I ever noticed those things. 

 They are easy enough to see when you know what to look for. I 

 thought at first you had reference to the planer marks." 



The white mahogany or prima vera (Tabebuia donneU»mithii) is 

 being tried out for propellers. This tree makes its best development 

 in southwestern Mexico and the northern part of Central America. 

 It is not closely related to the true mahogany, but belongs in the 

 catalpa family. The wood is of a light yellow color, rather fine and 

 uniform textured, usually with ribbon grain, takes a good finish 

 and has good cabinet qualities. It is somewhat lighter than aver- 

 age mahogany (specific gravity about .420) and in bending tests 

 has proved to be somewhat weaker. In hardness and compression 

 tests it exceeds most specimens of mahogany except the dense 

 grades. 



The woods sold as Philippine mahogany are causing the propeller 

 makers and inspectors more trouble than all others combined, due 

 largely to the question of identification. Two general grades are 

 recognized, the red lauan and the tanguile groups. The latter is 

 used in training propellers, but no Philippine wood is now per- 

 missible in the combat type. Since these woods have more or less 

 resemblance to the genuine mahoganies it is not surprising that 

 the manufacturers and inspectors to whom the woods are new are 

 finding it difficult to keep the species and grades separate. 



The name Philippine mahogany applies to a whole group of woods 

 ■which belong to a family known as the dipterocarps and which are 



not related to the real mahogany. In their native markets the 

 woods are not permitted to be sold as any kind of mahogany, but 

 unfortunately this rule does not apply to the export trade. Most 

 of them belong to the genus Sliorca, which includes about twenty 

 species, about one-half of which arc of commercial importance. The 

 writer has given these woods considerable study, and if there is 

 any means whereby the different species can bo separated with cer- 

 tainty he has yet to know of it. The problem is almost identical 

 with that presented by our southern pines, whose woofls so inter- 

 grade that botanical distinctions liave to be put aside and the 

 material classified according to its quality. The Philippine woods 

 show as wide a variation within the species, depending upon the 

 conditions under which the trees grow. Tanguile from the province 

 of Bataan is reputed to be the best, hence the names "Bataan 

 mahogany," "Bataan tanguile," or merely "Bataan." For prac- 

 tical purposes red lauan includes the lighter grades and tanguile 

 the heavier and stronger kinds of the so-called Philippine mahogany. 

 The principal objections to Philippine mahogany are the difficulty 

 of seasoning, the tendency to warp and check, and the rather poor 

 cabinet qualities. Some grades are very harsh and almost impossi- 

 ble to finish smoothly. In fact some cabinet makers can identify 

 such grades in the dark by merely passing their fingers lightly along 

 the planed wood, for no matter how carefully it is worked down 

 the natural wood will feel prickly against the grain. When prop- 

 erly finished, however, the wood presents an excellent appearance. 

 The separation of Philippine mahogany from the genuine offers 

 no difficulty to anyone who is willing to take a little trouble to 

 master a few details. In the first place the pores have no red gum 

 in them, such as one finds in Cedrcla, Smctenia and Kliaya. Of still 

 greater value are the resin ducts, which are as characteristic of the 

 dipterocarps as they are of the pines. These appear in narrow white 

 lines or circles, sometimes like growth rings, sometimes very short 

 and irregularly disposed. If the end of a piece is cut smoothly with 

 a sharp knife and examined with a hand magnifier it will be noted 

 that these white lines are like rows of little white beads, each bead 

 corresponding to the end of a resin duct. As previously stated, 

 some of the hard mahogany has its pores filled with lime, but these 

 will not be confused with the resin ducts just mentioned if it is 

 remembered that the ducts are characteristically in tangential rows 

 instead of being scattered about as the pores are. The trouble 

 with such characters as this is that most people identify woods 

 only by the general appearance and do not take the pains to make 

 use of the finer distinctions employed by the wood technologist. 

 With the increase in the number of foreign woods on our markets 

 and the likelihood that this is only the beginning it would seem 

 that now is a good time for the wood-user to get more closely 

 acquainted with his material. To this end a small hand magnifier, 

 a sharp knife, and a disjiosition to use them are ijidispensable. 



The Fertilizing Value of Ashes 



AVIiile we have some data of the quantity of potash recovered 

 from wood ashes in this countr.v and are encouraging conservation 

 and use of ashes for fertilizing purposes, in Italy and other parts 

 of Europe this matter has been gone into more thoroughly and more 

 specific data is at hand as to the actual fertilizing and money value 

 of ashes. 



In Italy statistics have been compiled showing that as a rule 

 one ton of different woods produces the following quantities of 

 ash and potash. 



Wood Ash Pounds Potash Pounds 



Kim 55.11 8.60 



Oak 29.76 3.31 



Beech 12.78 2.80 



Ash 26.90 1.63 



Spruce 7.50 1.00 



It is figured that there is an average of from six to ten per cent 

 of potash in wood ash. This and the value of the potash are de- 

 termining factors in the value of wood ashes. 



