The items in this cost are: Six men, at $1.75 per day, $10.50; 1 team, at $4.50 per day, $4.50; 1 cords of fuel, $5; and miscellaneous expenses, including wear and tear of apparatus, $2.50. To the above cost of 45 cents per pole must be added the cost of the preservative absorbed by the average pole.

RESULTS.

QUANTITY OF PRESERVATIVES ABSORBED.

Tables 1 and 2 give in detail the absorption of the several preservatives and the average cost per pole with the brush treatmentTable 1 for cedar poles at Wilmington, N. C., and Table 2 for chestnut poles at Pisgah, N. C., Dover, N. J., and Thorndale, Pa. Table 3 shows the average absorption and cost of treatment of chestnut poles at Dover and Thorndale by the open-tank method.

TABLE 1.-Brush-treated cedar poles at Wilmington, N. C.

For analyses and manufacturers' directions for applying the various preservatives see Appendix I. Cold.

c Hot.

TABLE 2.-Brush-treated chestnut poles at Pisgah, N. C., Dover, N. J., and Thorndale, Pa.

One hundred and eighty-four chestnut poles were treated in open tanks at Dover, N. J., and Thorndale, Pa. Of these, 160 were sea

soned and 24 green. Table 3 gives the total number and the average absorption and cost of treatment per pole in each season's cut of seasoned and green poles.

TABLE 3.-Tank-treated chestnut poles at Dover, N. J., and Thorndale, Pa.

There was a wide variation in the amount absorbed, as may be seen from the maximum and minimum runs of the spring, summer, and

autumn cuts.

Table 4 shows the maximum and minimum runs of the spring, summer, and autumn cuts. Only two runs of winter-cut poles were included in the tank treatments, and this season's cuts are therefore not given.

TABLE 4.-Absorption of each pole in maximum and minimum runs on spring, summer, and autumn cut chestnut poles.

The maximum absorption by any one seasoned pole was 44 pounds and the minimum 8 pounds. The maximum absorption by any one green pole was 18 pounds and the minimum 4 pounds.

Although it appears from Table 3 that spring-cut poles absorbed more preservative than any other season's cut, it is hardly safe to accept it as a general fact, because of the small number of poles used in the experiments and the variation between the individual runs. However, the increased absorption of the spring-cut poles agrees with the results of the seasoning experiments set forth in Circular 103, which showed spring-cut poles at all stages to have contained less water than poles cut at other seasons.

Experiments are now being carried on by the Forest Service to determine with certainty the relation of season cut to absorption.

ABSORPTION INCREASED BY SEASONING.

It was found that the more thoroughly the pole is seasoned the deeper and more uniform is the penetration and the greater is the absorption. This seems to be equally true in both brush and tank treatments. From page 11 it will be seen that the seasoned poles absorbed nearly twice as much preservative as the green poles.

ABSORPTION UNAFFECTED BY SOAKING.

In this series of experiments the only opportunity to study the effect of water-soaking on the absorption of the preservatives was at Wilmington, N. C., where all of the preservatives were applied by the brush method.

Here it was impossible to note any difference in absorption or penetration on poles which had been soaked over those which had not. Other experiments of the Forest Service where different methods of treatment have been tried bear out this same conclusion.

EFFECT OF SEASON OF CUTTING ON ABSORPTION.

In the brush treatments it was impossible to note any characteristic difference in absorption or penetration due to the season of cutting. In the tank treatments, where only one preservative was used, the difference seems to be quite marked. The spring-cut poles absorbed the most, and the cuts of winter, summer, and autumn follow in the order given. This agrees with Circular 103, which shows the spring and winter cut poles to lead in the progress of seasoning.

EASE OF APPLICATION.

Brush treatment.-Those preservatives which solidify at low temperatures are least easy to apply. This is especially true when the

treatment is made in cold weather. The low atmospheric temperature will cause the preservative to solidify when it strikes the pole and thus prevent a good penetration. The second coat, although applied hot, often fails to melt the first and penetrate the pole, but remains on the outside to be scraped off or melted off at the first rise of temperature.

Open-tank treatment.-The effect of air temperature upon the preservative is less important when the open-tank process is used. In this case the preservative in contact with the pole is kept liquid by heat. As only one preservative was used in this process, no opportunity was given for comparison. Yet from other experiments it might be stated that in general the thinner the solution the easier is its application, provided a temperature above the boiling point of water can be maintained without the loss of the preservative by evaporation.

METHOD OF APPLICATION.

Brush treatment.-In most cases a better penetration is secured by applying the preservative hot than cold. The degree of temperature necessary depends largely upon the extent to which the wood is seasoned. In well-seasoned wood all that is required is that the preservative be thoroughly liquid. In partially seasoned or unseasoned wood a higher temperature is essential to secure the best penetration. In most cases a temperature above 200° F. is inadvisable; this is especially true when the preservatives employed contain oils having a low boiling point, since such oils evaporate very readily upon being spread over the pole.

Open-tank treatment. In this process, where it is necessary to hold the temperature above the boiling point of water for several hours, it is advisable to use a preservative containing few or none of the light oils, since liquids which by the usual method of analysis distill off but a very small per cent below 400° F. have decreased very considerably by evaporation when held between 212° and 275° for several hours. When the temperature was raised above 275° the outer portions of the poles were more or less scorched.

DEPTH OF PENETRATION SECURED.

Brush treatment.-A penetration of from two to three annual rings, ranging from one-sixteenth to one-fourth of an inch, was secured. The penetration seemed to be slightly greater in chestnut than in cedar.

Open-tank treatment.-The average penetration by this process was about one-half inch. In open-grained, porous wood, and in that

which was slightly doty or defective, it was somewhat greater, reaching a maximum of from three-fourths of an inch to 1 inch, while in close-grained, dense wood the penetration was from one-fourth to one-half of an inch.

PROBABILITY THAT TREATMENT WILL PAY.

Though the length of time added to the service of these poles can not now be stated, enough is known regarding the value of the preservatives as preventives of decay to justify a conclusion as to whether the added life will repay the cost of treatment.

FIG. 2.-Untreated chestnut pole, showing decay at ground line after six years' service. (Drawn from a photograph.)

By the brush method the average cost per pole was about 40 cents, or 29 cents in the case of creosote, of which 7 cents stands for the cost of oil. By the open-tank process the average cost per pole with creosote (the only preservative used) was 67 cents, of which 22 cents stands for the cost of oil.

[Cir 104]