stock of the same thickness, if sawed and piled during the months of extremely hot weather, would have to be carried over until the approach of another summer, the effect of the season of extremely damp atmosphere seeming to be to liberate the internal moisture, which somehow appeared to be imprisoned by some (at that time) unknown force, and which, being so liberated, was rapidly carried off by the cool, dry days of the following spring.
It had probably always been known that lumber would dry, and did dry, most rapidly during the season of high winds, but the fact had been generally accepted without asking for a scientific reason. But when it dawned upon the minds of the experimenters that there must be one, it led to the further discovery that air in motion of a low temperature would produce better results than air of a high temperature if kept stagnant, and that the ordinary atmosphere, with its natural temperature, if above the freezing point and with a low degree of humidity, if kept in constant motion or circulation, would dry lumber well and rapidly without the aid of artificial heat.
These points once definitely settled and understood, led to researches that immediately led into the domain of wood chemistry and physiology, and the experimenters and inventors became to a degree chemists and physicists. Thus a special education was obtained before they were able to say they had solved the problem of drying lumber artificially; fairly accurate knowledge on the following points being gained:
1. (a) Different varieties of wood, and (b) wood of the same variety grown in different localities, requiring radically different treatment.
2. (a) That too high a degree of heat applied at any stage, and (b) especially during the first, injured the lumber more or less, according to kind, and retarded or prevented perfect drying.
3. That with a perfect circulation of air of a low degree of humidity, a high temperature was not necessary to produce good results except as to time.
4. That the results, good or bad, depended very largely upon the chemical changes produced by heat upon the natural gums and juices of the wood.
5. That all these points became much more pronounced in the case of hard woods, and hence the necessity for special machinery and arrangement of the kiln.
