47 



too deep into tlu' ciiviMcs. Ilence tlie dinereiice, and (lie neeessary elioice between tliein. Both 

 ways fiiiiiish vaiial)Ie results, tliese deinMidiiij;- in tlie case of tlie eali])ei' on aeeuraey of dressing 

 and precision in the management of a delieate iustrunient, and involving the danger of tmi (1^111)11 

 cat ed computation. In the case of the measurement by iinmcMsion the variations depend <in the 

 nature, form, and size of the piece of wood, but the nietliod is relatively free from the danger ot' 

 error accompanying the use of delicate instruments, inaccuracy of reading, and complicated com- 

 putation. 



DRYING. 



A^GV marking the pieces are left to dry at ordinary temperature. Then they are placed in a 

 <lr.\' kiln and dried at 100° C. 



The drying box used is a double-walled sheet-iron case, lined with asbestos paper and healed 

 with gasoline. The air enters below and has two outlets on top. The temperature is indicated by 

 a thermometer and maintained fairly constant. 



The reason for clioosing thetemperatureatlOO'^C., or the boiling ])oint of water, is the fact that 

 experimenters generally have used this particular temperature, and for the sake of com])arableness 

 of results the continuance of this practice is desirable. To Judge from the experiments so far 

 made, this tenipiTature is taken somewhat too high. Prof. Baiischinger, of Mtinich, describes 

 similar experiments where the wood at this temperature lirst grew lighter and Anally increased 

 again in weight. The same thing has been observed in our work, but neither the cause nor the 

 nature of the process has as jet been determined. Moreover, the wood is brought too near the 

 burning point and danger from conflagration is great. Besides these two chief objections it may 

 be argued that wood in all ordinary uses is never subject to teui])eratures ninch above (!()' ('. 



To determine the difference in liuniidity of wood dried at different tempi'raturcs, and to obtain 

 moistiu'e-coeflficients corresponding to the different temperatures, some experiments weic made un 

 the wood of the white i)ine and that of the longieaf pine. For one of these, i)ieces of sapwood, 

 split nearly as thin as matches, were used. Tliese were tied in loose bundles, weighed, then i)laced 

 in the oven to dry. 



The following figures contain the priucii)al results: 



Woiplit bi'fore plaoing in kiln 



Dried .-it 60 to 62" C 



Dried atun to 82° C 



Dried at 100 to 105° C 



V, palnstris. 



7.1.5 

 (!8.4 

 67.5 



ce.9 



P. Strobnx. 



Gram». 



.■)5. 4 

 :);;. 3 

 :i2. 8 



33.5 



From these results the humidity expressed as percentage of dry wood dried at varying de- 

 grees is : 



p. paliiutris. 



P. Slrobus. 



At ordinary temperature (.about 25° C) 



Dried at abnutnnoc 



Dried at about 80° C 



Dried at about 100° C 



Gramt. 



Oravu. 



8.1 



2.4 



.0 



.U 



Though this problem is by no means solved by these few experiments, it is clear that a lower 

 temperature than KH)'^ 0. would have served .just as well, and al.so that wood drieil at 80° ('. (a 

 much safer temperature) is nearly as dry as that dried at 100° C. 



MOISTURE EXPERIMENTS. 



In connection with these exi)criments in drying at different temperatures a .series of exjx'ri- 

 ments on the shavings of the sapwood of white pine and longieaf ])ine were made ; one to detei'inine 

 the amount of nioi.stnre which shavings of this kind aic caiialilc of taking nji, another to dctei'mine 

 the daily changes going on in the humidity of wood, I'^or the Ijrst of these, air dried >liavin^s of 



