46 



A neatly dressed piece of white pine was measured with caliper and its dimensions in centi- 

 meters found to be as follows : 



Width (one side) 



Wirttli (other side) 



Heijilit (one side) 



Hei;;lit (otlier side) 



Av<-rage lengtli 



Average wid"tb 



Average heiglit 



Volume cm^ 



Volume by immersion 



Ditierence cm 



Ouo end. 



4.528 

 4. 48U 

 4.538 

 4. .'J24 

 15. :i80 

 4. 405 

 4.527 

 312. 983 

 309. 700 

 3. 265 



Middle. 



4.520 



4.476 



4. rao 



4.538 



Other end. 



4.504 

 4.464 

 4.524 

 4. 508 



After 8 minutes of immersion : 

 Volume by immersion: 310.8, first trial. 

 Volume by immersion : 310.9, second trial. 



The surface area of this piece is in round figures 318 cm^, of which 40 fall to the ends. If the 

 difference, 3.2G cm' of water, were evenly distributed over this area, the sheet of water soaked 

 or rushed in would be but 0.01 cm., or 0.1 iniii., or 0.001 inch thick. 



Again, the end surface is 10 cm., the density of the piece about 0.10; setting the density of 

 wood substance at about 1..5(J, one fourth of this surface is cell-wall, the other throe fourths cell- 

 lumen. According to the calculations set forth above, the sheet of water drawn into the cut lumina 

 of the cells is less than 1 mm. thick. This when .spread over three-fourths of the 10 cm-, or 30 

 cm^, would account for nearly 3 cm^ of water. 



In a third experiment, on apiece of fresh oak wood, the volume by immersion was found to be: 



720 cubic centimeters First trial 



729 cubic centimeters Second trial 



730 cubic centimeters Third trial 



730 cubic centimeters Fourth trial 



730 cubic centimeters Fifth trial 



These experiments show that the water in filling all crevices and pores does not proceed uni- 

 formly; that its progress depends on variable circumstances, of which the form and dimension of 

 the cavities and the existence of a film of air are probably the most important. Tliey also indicate 

 that, whether fresh or dry, the water adapts itself to the configuration of the wood, a cover sheet 

 is formed which adheres to the wood and is held tliere by a capillary attraction, but that the water 

 does not rush Into the wood in a manner analogous to that observed in inorganic porous bodies. 

 In every case the measurement of the caliper is greater than that found by immersion. 



The ([uestioii now arises, is the measurement by immersion, with its variable factors, suffi- 

 ciently reliable or should the volume be determined by tlie caliper? To decide this question it is 

 necessary to examine the latter method itself. In doing so we may ask, is it more accurate, and 

 is it practicable? Turning back to the calijier measurements recorded above, we find that in a 

 soft, well-dressed piece of wood the dimensions varied veiy considerably. The height, for in.stance, 

 was on one side 4.524 at one end, 4.538 at the middle, and only 4.508 at the otlier end. Comparing 

 this with measurements made on machine-planed pieces of molding, etc., it was found that the 

 latter varied as much— in some cases even more. None were free of the wavy outline so charac- 

 teristic of machine i>laning. The end surface produced bj^ a saw-cut requires no mention, for every 

 one is familiar with its appearance. To be reliable, then, much more accurate work in dressing 

 would be requisite. 



The practicability of this method is limited to pieces which can first be accurately dressed ; fresh 

 woods, checked pieces, etc., are thus excluded. The time requisite to determine the volume can 

 easily be estimated when we consider that fifteen measurements, each requiring the use of the 

 magnifier and the delicate adjustment of the micrometer instrument and nine arithmetical proc- 

 esses, were retjuisite to find the volume of one piece of wood. 



From the above we see that the caliper measure is preferable only if the piece is dressed and 

 (pressed perfectly. As it is, the caliper measures the wood only at its projections, the water presses 



