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288 Institute of Technology to determine the quantitative effect, if possible, of such conditions. While Douglas fir (Pseudotsuga Douglasti) has been known and used for a little over 50 years in shipyards, usually in the east under the name of Oregon pine, it is only with eae Se eee ee Poe >» a a 1 a Pq Ww > fe) a < et z Wi re) ec w a Ww a =) | my ° = | Zz 2 EF Oo a re) ro) o < Bake c End of Block 2 PENETRATION, INCHES FIG. 2—REABSORPTION OF SPECI- MENS WHEN EXPOSED TO SATURATED AIR AT 120 DE- GREES FAHR. P-r indicates pine treated 1 hour; F-9 fir treated 9 hours; other symbols to be similarly interpreted the recently increased transportation facilities that it has appeared in such quantities as to necessitate that it be reckoned with in the East as a struc- tural timber. This fact led the experimenters to make a parallel investigation for the purpose of comparing this Douglas fir with southern hard pine. In so far as the writer is aware, this is the first work of the kind to have been done on Douglas fir. The pine used falls under the classification of “dense south- ern pine” according to the standards of the American Society for Testing Mate- rials and is very probably the long-leaf yellow pine (Pinus palustris). Nature of the Investigation The tests were carried out, it is true, upon small specimens and in consequence are open to criticism such as has been made concerning much of the work which has been done by the bureau of forestry. It must be acknowledged that the results are scarcely to be used as constants of design, but it is believed that they may well be used as _ indica- tive of certain truths and as a means of comparison in the guidance of the users of the two timbers placed under observation. The investigation under discussion may be briefly outlined as follows: The stock used had been purchased in the open market without any special care THE MARINE , REVIEW in selection. In the form of 4-inch planks it remained in the testing labora- tories about six months under the con- ditions of heat and moisture ordinarily pertaining to such localities, being open to free and complete circulation of air over and around the material. Tests showed the moisture content to be between 6 and 8 per cent for all pieces. The timber, then, may be con- sidered to have been thoroughly air- dried. From these planks were cut specimens which were planed to a sec- tion 2x2x20-inch. These pieces were cut further into blocks 8 inches long, and the pairs thus obtained were used in most cases under similar conditions of treatment for check purposes. All treatments were conducted on speci- mens 8 inches long and tests were made on specimens 6 inches long formed by the removal of 1l-inch from each end of the treated specimen. A number of specimens of both pine and fir were tested in the air-dry condi- tion to establish their initial properties. One set consisting of 20 pieces of pine and 20 pieces of fir was subjected for various lengths of time to a saturated atmosphere at 120 degrees Fahr. An- other similar set was immersed in fresh water at 70 degrees Fahr. for various periods of time. The relative rates of moisture penetration and the properties of the wood as determined by direct compression in a direction parallel with the grain were investigated and the re- sults appear later in this discussion. The moisture determinations were made as follows: From the blocks were cut sections approximately %4-inch thick. Six of these were cut from the first 1% inches of length and a seventh from the center. See A, Fig. 1. It was necessary to eliminate the effect of lateral penetration of moisture, conse- quently the outer %4-inch was removed from these sections with a. chisel, as indicated at B, Fig. 1. The relatively slow lateral penetration as shown by various tests made by the bureau of forestry would indicate that this was sufficient precaution. In. order. to eliminate or at least minimize the effect of evaporation from the end grain, the sections were cut with the greatest expedition possible with a hand saw in a miter box and then immediately placed between clean glass plates. The edges were trimmed and the initial weighings made with the least. possible delay. The moisture content was obtained in the usual manner. After removal of all adhering dust and ‘splinters, the sections were carefully weighed. _ They were then exposed to a reasonably dry air bath at 212 degrees Fahr. This temper- ature is necessary to effect the complete removal of the moisture. Care must be taken that the temperature does not exceed this value, because of the possi- bility of a loss in weight due to the REABSORPTION— MOISTURE PER CENT ABOVE AIR-ORY July, 1918 evaporation of some of the more volatile oils. It is probably true that some slight distillation may occur even at 212 degrees, but it is likewise probable that some slight moisture remains, even when the sample has been dried to a constant weight at this temperature. The known facts seem to justify the assumption that one of these effects very largely counterbalances the other, or at least that any existing discrepancy is of a magnitude negligible in this dis- cussion. Oven-Dry Weight The drying is continued until a con- stant weight is obtained. With samples of this size and form, taken from the woods under consideration, this con- stant weight is generally obtained in about 1% hours. This is known as the oven-dry’ weight. The loss in weight under the fore- going conditions, divided by the oven- dry weight, expressed as per cent, gives the moisture content. While the moisture even in so thin a block as those investigated will doubt- less vary from surface to surface, yet it seems sufficiently accurate for the purposes of this paper to take the average value as representative of the conditions at the center of the section. These values have been so assumed and Q { $s & Endof PENETRATION , INCHES FIG. 3—REABSORPTION OF SPECI- MENS WHEN COMPLETELY IM.-.. MERSED IN FRESH WATER AT 70 DEGREES FAHR. P-24 indicates pine treated 24 hours; F-48, fir treated 48 hours; other symbols to be similarly interpreted are plotted in the curves of Figs. 2 and 3. : In any discussion dealing with the effect of moisture on the characteristics of wood it is very essential to have in