Saw Mills Their Arrangement And Management And The Economical Conversion Of Timber PDF Download

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1896 edition. Excerpt: ... the opposite side. This method of drying does not warp or discolour the wood, and is a preservative against dry rot. Some valuable experiments on the action of steam on various kinds of wood were made by M. Violette, a Frenchman, some years back. The woods treated were oak, ash, elm, walnut, and fir, specimens of which he submitted to the action of a current of steam at a temperature of 100 Centigrade, gradually raising it to the different points of 125, 150, 175, 200, 225, 250, without the addition of any water, so that the vapour was no longer saturated, but was rendered capable of extracting the moisture contained in the wood. Portions of the various woods were weighed and exposed to these temperatures for two hours in closed chambers, and again weighed when cool, in order to find the amount of loss of weight by desiccation. This loss was found to increase in a constant ratio according to the temperature; but great variations were experienced with different woods. At the temperature of 175 elm and oak lost one-third of their weight, and at 250 one-half; ash and walnut lost one-fifth at 175, and two-fifths at 250; and fir, one-sixth and one-third at the same temperatures. Until the heat reached 175 they each preserved their primitive colours, but from that point to 200 a slight change took place. Above 200 the colour gradually deepened, and at 250 oak became black. This change of tint indicates the formation of tar in the wood, which seems to be necessary for its due preservation. The particular result of these trials to which we would direct the attention of the worker in wood is the great increase in strength which this treatment causes; this has been accurately determined at the different degrees of temperature, showing the...