DeCEMHEK 12, 189c. j 



SCIENCE. 



327 



ularlj true when weak solutions are used; and when the potency 

 is greatly increased, the tenacity of the timber is impaired. In 

 Germany 1.91 jjer cent is considered the proper strength lor rail- 

 way-sleepers Several sugsestions have been made to confine the 

 zinc in the timber. Mr. W. Thelmany proposed to subject the 

 timber to a subsequent bath of chloride of barium, with the view of 

 producing an insoluble sulphate of baryta. It is doubtful, how- 

 ever, if the re-3Ctiou would go on in the minute sap-ducts of the 

 wood. Another process is that of Mr. Wellhouse, who also 

 employs a double solution, the first being chloride of zinc to which 

 a little glue is added, and the second a solution of tannin. It is 

 claimed tl;at the latter, upon coming in contact with the glue, 

 forms small particles or films of artificial leather, which plug up 

 the mouth of th? sap ducts, and prevent the zinc being washed 

 out. Certain experiments which have been made seem to confirm 

 the idea. Another plan consists in using a solution of chloride of 

 zinc and gypsum. The gypsum crystallizes and hardens inside 

 the sap-ducts, and forms partitions to hold the zinc within the 

 cells There are three bumettizing works in the United States; 

 and the cost of the process is about 6ve dollars per thousand feet 

 board measure, or from twenty to twenty five cents a sleeper. 



Creosoting is so well understood that it scarcely needs descrip- 

 tion. It is in almost universal use for sleepers for English rail- 

 ways, and no other process has been commercially proved capable of 

 resisting the Teredo navalis and Limnoria tenebrans. In England 

 and Holland from ten to twelve pounds of creosote-oil per cubic 

 foot of timber are found sufficient for harbor purposes; the 

 French use nineteen pounds for the same purpose; and a similar 

 quantity has been found necessary in the Gulf of Mexico, where 

 the marine worms cut off an unprepared pile in eight months. 

 The creosoting process needs to be well done to be effective, and 

 for ordinary purposes from eight to twelve pounds are requii'ed 

 per cubic foot of timber. 



It was generally considered that the presence of heavy oils in 

 the creosote was objectionable, and therefore engineers were ac- 

 customed to specify that not more than 10 per cent should be 

 present. This view has been controverted by others, who take 

 the view that it is only the heavy oil which can be relied upon to 

 exert a continuous preservative action, the creosote itself being 

 liable to become dissipated in course of time. This view receives 

 confirmation by the good results of the preservative process intro- 

 duced by Mr. Henry Aitken of Falkirk. This consists simply in 

 soaking timber ia melted naphthaline for a period varying from 

 two to twelve hours, depending on the bulk of the piece. A 

 temperature of ISO"^ to 200° F. is all that is required for the pro- 

 cess, and is most easily obtained by placing steam-pipes in the 

 bottom of the tank which contains the material. Simple as the 

 process is, that is not its chief merit. A more valuable feature is 

 that it can be applied to green timber-, thus doing away with the 

 long and expensive process of seasoning. The naphthaline makes 

 its way through the pores of the wood, decomposing the albumi- 

 noid compounds, and displacing both sap and water. It then 

 becomes fixed, and the whole substance is permeated with solid 

 antiseptic of a permanent character. 



Aitken's process was introduced in 1883, and three years after- 

 wards an account was given in Engineering (July 3, 1885) of cer- 

 tain trials that had been made to demonstrate its utility. Among 

 these were mentioned the construction of some railway-wagons 

 for the North British Railway. These were made from logs taken 

 direct from the timber-pond and naphthalized. The logs were cut 

 up and worked in the usual way ; for, unlike creosoting, the Aitken 

 process does not render timber more difficult to cut, neither does 

 it interfere with painting or varnishing. The wagons have, up 

 to the present, shown no signs of decay, and all the joints are 

 tight. When taken apart, the tenons still show the chisel marks, 

 demonstrating that they have not been working in the mortises. 

 On the same railway there were placed sleepers and keys, and 

 after seven years these are still perfectly fiesh. One of these keys 

 is in perfect condition, and does not appear to have been touched 

 since it was first dri\ en. Four years ago fencing-slabs of poor 

 Swedish timber, some already beginning to decay, were naphtha 

 lized and put down, and to-day they are in as good a condition as 

 ever. 



In coal-pits equally good results have been obtained; and larcli 

 timbering, which usually becomes quite rotten in five years, has 

 remainpd perfect!}- sound. White atits and the Teredo donot find 

 naphthaline more palatable than creosote, for samples laid in the 

 harbor of Colombo have been carefully avoided by both pests. 



In England there are only two methods of preserving timber in 

 general use ; namely, careful seasoning and creosoting. The latter 

 is only applicable to rough work, such as sleepers, fencing-posts, 

 and the like; while the foimer is expensive, and is only moderately 

 successful ia the case of soft timber. II remains to be seen if the 

 Aitken process will take rank with the others and obtain general 

 acceptance. It is full of promise, and, if it fulfils only a part of 

 what appears to have been proved for it experimentally, will be a 

 valuable addition to the means of fighting the deteriorating in- 

 fluences of time and weather. For many purposes hard woods are 

 employed simply on account of their great durability; the cheap, 

 soft woods being, in other respects, equally well suited. If the 

 soft woods can have their lives prolonged, a great saving can be 

 effected in most cases. The sudden seasoning said to be effected 

 by naphthaline, without sensibly hardening the wood or rendering 

 it diflScult to work, deserves to be carefully investigated, as it. 

 would liberate an immense amount of capital now lying idle, be 

 sides preventing the annoyance resulting from the use of half- 

 seasoned timber. Every thing that offers to cheapen production 

 is worth trying in these times of fierce international competition. 



THE FORESTS OF ANNAM. 



The forests of Annam have recently, says the French Moniteur 

 Official des Commerce, been explored by one of the officials of the 

 Forests Department, who was instructed by the French Govern- 

 ment to examine and report upon them, particularly with refer- 

 ence to their extent and the possibility of their practical utiliza- 

 tion. The first information obtained upon the subject relates tO' 

 the forests of Nghe-An, in the province of Vinh. These forests, 

 says the Journal of the Society of Arts (London), quoting from the 

 above-named periodical, are situated in the mountains and at- 

 sorae considerable distance frona the coast, covering almost the 

 whole of the district watered by the Song Ca River, commencing 

 at Luong, and its principal tributary the Song-Cong. The lower 

 vegetation covering the soil, and the almost impenetrable network 

 of tropical climbers which reach up to the higher branches of the 

 trees, render it extremely difficult to penetrate far into the heart 

 of the forests. 



The woods met with in the forests of Nghe-An are very varied 

 and numerous; but the most important, and those in which con- 

 siderable trade is carried on, are the go-Hem, or iron wood, and 

 the govim-tam. The other descriptions of wood, although often 

 more valuable, are much rarer, and therefore less frequently met 

 with on the various markets. The go-Hem, or iron wood, is hard 

 but brittle, of a brownish-red color, and would last a very long time 

 were it not for the injuries inflicted upon it by white ants, which 

 attack and speedily destroy it. In spite of this, it is eagerly sought 

 after, and is of great utility, being employed in the construction 

 of columns for pagodas and houses, piles for bridges and plat- 

 forms, furniture, coffins, junks, etc. Its weight is about I.IOO 

 kilograms the cubic metre. It takes a good polish, and hardens 

 in course of time. It is brought to market in logs of from five to 

 eight metres in length, and sometimes, but less frequently, from 

 ten to twelve metres in length. The go-Hem is largely e.xported. 

 The go^an-tam'K a yellowish-white wood, with a very fine grain. 

 It is easily worked, is very light, and polishes well. It is used 

 for the common kind of furniture, mouldings, boxes, and ordinary 

 coffins, the hulls of junks and sampans, oars, etc. Its most fre- 

 quent use is in ship-building. 



Beyond these two descriptions, which, from a comineriial point 

 of view, are the most important, there are a number of other 

 woods little used by the Aniinmites, either on account of their 

 scarcity, or iiecause they are considered to be little capable of be- 

 ing worked up. They are, however, says M Thomfi, well deserv- 

 ing of .«ome attention, by reason of the fact that Europeans 

 might find a use for this excellent taw mtterial which the Asiatic 

 appear incapable of doing. 



