Page:Popular Science Monthly Volume 45.djvu/394

378 thing only was known—that heat would drive the moisture, whether natural or acquired, out of the lumber, if it was only applied hot enough and long enough.

The physiology of wood, or what is now known as timber physics, was poorly understood by any one, much less by the men who were making the experiments; for in general they were plain business men, with only ordinary business education, and with no pretensions to scientific knowledge.

Thus little or nothing was known of the chemistry of woods and absolutely nothing of the effect of heat upon the gums, juices, or fibers. But while these men were not up in the sciences, they possessed what perhaps in this instance stood them in as good stead—hard common sense and quick perceptions, that permitted them to learn rapidly by experience and by quickness of observation to note the results upon the woods of various conditions in the course of their experiments.

Thus it was discovered, by a more or less costly experience, that in all the long list of varieties of timber hardly any two could be subjected to precisely similar treatment with the best results to both; and it was further found that difference in the source whence the same variety came often required a variation in treatment.

The next and perhaps the most important discovery made, and probably at the expense of the greatest amount of spoiled lumber, was that a temperature too high at the commencement of the drying process produced unsatisfactory results, and often ruined or greatly reduced the value of high-grade and costly material. Before this fact was discovered, so uncertain had been the process in its effects, other than in producing apparently dry lumber, that an actual prejudice arose against submitting upper grades to the artificial process until fairly weather-dried; it being found that if a portion of the moisture on and near the surface was evaporated by the natural heat of the sun, the effect of plunging the lumber at once into a high temperature when put into the kiln was less injurious.

Investigation and experiment proved further that this was a perfectly natural theory and one by which Nature herself worked constantly. It was fully and satisfactorily shown that lumber sawed and piled in the winter so as to take advantage of the first cool, dry days of spring, not only dried in better condition, with much less danger of sap stain, checking, and warping, but that it actually dried more completely to the very center of the piece, and in a shorter time.

This was found to be especially true of thick lumber, it proving to be a fact that, while the winter-sawed thick stuff would often, in favorable seasons, become remarkably dry to the very center.