ORGANIZATION OF THE FOREST SERVICE. GIFFORD PINCHOT, Forester. OVERTON W. PRICE, Associate Forester. P. P. WELLS, Law Officer. HERBERT A. SMITH, Editor. GEORGE B. SUDWORTH, Dendrologist. Grazing.-ALBERT F. POTTER, Assistant Forester, in Charge. Operation.-JAMES B. ADAMS, Assistant Forester, in Charge. Accounts.-GEORGE E. KING, Chief. CLYDE LEAVITT, Assistant Chief. Engineering.-W. E. HERRING, Chief. Lands.-GEORGE F. POLLOCK, Chief. Silviculture.-WILLIAM T. Cox, Assistant Forester, in Charge. Extension.-SAMUEL N. SPRING, Chief. Silvics.-RAPHAEL ZON, Chief. Management.-E. E. CARTER, Chief. W. G. WEIGLE, Assistant Chief. Products.-WILLIAM L. HALL, Assistant Forester, in Charge. Wood Preservation.-CARL G. CRAWFORD, Chief. FIG. 1. Diagram of an experimental tank used for treating fence posts--- 2. Diagram of an experimental tank used for treating telephone (3) THE OPEN-TANK METHOD FOR THE TREATMENT OF TIMBER. INTRODUCTION. When the preservative treatment of timber was first introduced into this country, the lumber situation was wholly different from what it is now. There was a seemingly exhaustless supply of structural timber of the finest grades, and hence the preservative treatment of timber for different uses was economical only in the comparatively few cases where the cost of renewals was unusually high. As the supply of timber gradually diminished under the enormous inroads made upon our forest resources by the industrial development of the country, the prices of the better grades of timber doubled and trebled, until it is now difficult in many places to obtain regularly an adequate supply at any price. The increased cost of material has made it necessary to use less durable but more plentiful timbers, which require some form of artificial treatment before they can be expected to give as long service as the more durable woods. Hence the amount of timber subjected to artificial preservation has greatly increased, and the number and capacity of treating plants throughout the country have increased accordingly. Most of the processes in general use require elaborate and expensive plants, consisting of closed retorts capable of withstanding high pressures, of vacuum and pressure pumps, steam boilers, etc. Such plants are usually stationary. The high cost of erecting them requires that they be located where the supply of timber will be continuous. This frequently means that timber must be transported long distances and double freight charges paid. Moreover, the interest on the investment and the cost of operating make it impracticable in most cases to use such plants for the treatment of timbers which are required in large quantities and at a comparatively low cost. There has thus grown up a demand for some cheap and simple process of wood preservation adapted for timber in common use, for which the pressure methods are too expensive. The general adoption of such a process would largely increase the amount of timber artificially preserved, and so result in a great saving in the amount of timber consumed annually in the United States. It would insure the more complete utilization of the forest products, and encourage the use of many so-called "inferior," or quickly decaying, woods for purposes for which only high-grade, or decay-resistant, woods are now almost exclusively used. [Cir. 101] HISTORY OF THE OPEN-TANK METHOD. There have been many attempts to find a cheap and effective preservative process requiring no costly mechanical equipment. Most of these attempts were founded on an unsound theoretical basis, and many of them failed for other reasons. Obviously one of the simplest methods of securing a penetration is to boil the wood in the preservative, and this method has been frequently employed. It was not, however, until the year 1867, when Prof. Charles A. Seely, of New York, discovered and patented the process which bore his name, that the true value of the boiling method was ascertained. Through Seely's attempt to increase the penetration by immersing the timber in a bath of cold preservative after it had remained for some time in the boiling liquid was discovered the principle which later developed into the open-tank method of to-day. Apparently, however, Seely's investigations attracted but little attention at the time, and though some writers assert that his method was used in various parts of the United States, no record can be found to-day of its application on a commercial scale. It appears to have been practically abandoned after a few years. At the Louisiana Purchase Exposition a series of experiments was undertaken by the Forest Service to determine some practical method of prolonging the life of fence posts. The expense of treating such timbers by the pressure processes was prohibitive; yet the receding of the forests, the agricultural development of the country, and the fencing in of large quantities of grazing lands in the West had depleted the supply of posts for farm purposes and raised their price. In the St. Louis experiments, boiling the posts in a vat containing tar oil was at first attempted, with only fair results, but in the course of the tests to increase the penetration the principle of the method once employed by Seely was revived. Subsequent developments in the experiments in which the Forest Service has applied this principle have resulted in what is now known as the open-tank method. WHAT THE OPEN-TANK METHOD IS. As already suggested, the open-tank method is based upon the use of an open tank, capable of withstanding heat, and either equipped with steam coils or so arranged that fire can be placed underneath. Sufficient preservative is run into the tank to cover the portion of the timber which is to be treated, and the temperature of the liquid is then raised slightly above the boiling point of water. This temperature is maintained for a length of time depending upon the character of the wood and the treatment desired. At the end of the hot bath the timber is either quickly transferred to another vat, containing a cold preservative, in which it is submerged for a definite |