42 



EXAMINATION INTO THE PHYSICAL PROPERTIES OF TEST MATERIAL. 



(Written by Filibekt Koth.) 



The physical' examination consists in ascertaining the specific weight of the dried material, 

 and incidentally the progress and amonnt of shrinkage due to seasoning; the counting and 

 measuring of the annual rings, and noting other microscopic appearances in the growth; the 

 microscopic investigation into the relation of spring and summer wood from ring to ring; the 

 frequency and size of medullary rays; the number of cells and thickness of their walls; and, in 

 short, the consideration of any and all elements which may elucidate the structure and may have 

 influence upon the properties of the test piece. The rate of growth and other l)iological facts 

 which may lead to the finding of relation between physical appearance, conditions of growth, and 

 mechanical properties, are also studied incidentally. 



CONDITION OF THE MATERIAL ON AKKIVAL. 



The specimens sent by mail, and in double wrapper, oiled paper inside, have arrived in all 

 cases in very good condition. The journey from Alabama to Michigan occupies from two to four 

 days, and only in exce])tional cases arc the wrajipers worn. To determine the effect of the wrap- 

 per as a preventive against evaporation, several pieces were allowed to remain in their original 

 wrapper, and were thus weighed from time to thne. 



The following figures refer to a half disk of Pinun palustris, consisting almost entirely of 

 sajjwood. 



Date. 



Oct. 24.... 

 Oct. 20 ... . 



Oct. 30 



Oct. SI ... . 

 Nov. 2.... 



Loss (2.2 per cent) 

 Dec. 12 



Loss (17.2 per cent) 



Weight of 



l)i(H'f! 



including 



1,607 



1,600 



1,572 



1.572 



1,568 



39 

 1,330 



Kemarks 



ler rubbed oft' at one corner. 

 I'hiced on a ahelf 10 feet from a steani-licitinK coil. 

 AftiT weighing to-dav a ilanip cloth w a.s placid over the piece. 



Cloth remaineil, but was not renioi-stencd ; it therefore became dry and wan removed. 

 The piece felt moist and was covered with inuld. 



During the same time a piece of the same disk and weighing 823 grams at first, was left 

 without a wrapper in an unheated room and lost 298 grams or 3G.1 per cent. These figures 

 show that the wrapi)er alone reduces the evaporation to a minimum, which may well be left out of 

 consideration, and also that if this wrapper is reinforced by dampened cloth, a precaution always 

 observed during the time of working up the specimens, the evaporation ceases entirely. 



SHAPING AND MAKKTNG OF THE MATERIAL. 



The obiectof this work being in part the di.scovery of the differences that exist in the wood, not 

 only in trees of different s))ecies or of the same species from various localities, but even in the wood 

 of the same tree and from the same cross section, a careful marking of each piece is necessary. 

 The disks are si)lit, first h\U> a north and south i)iece, and each of these into smaller pieces of vari- 

 able size. Ill one tree all pieces were made but ;! cm. thick radially, in another 4 cm., in still others 

 5 cm., while in some trees, especially wide-ringed oaks, tlie pieces were left still larger. In the 

 conifers the outer or first piece was made to contain only sapwood. Desirable as it appeared to 

 have each piece contain a certain number of rings, and thus to represent a fixed period of growth, 

 it proved impracticable, at least in the very narrow-ringed disks of the pines, where sometimes the 

 width of a ring is less than 5 mm. (0.2 inch). 



Some of the disks were split to a wedge shape from center to periphery, so that each smaller 

 piece not only reitresents a certain period of growth in ([uality, but also in quantity, thus simplify- 

 ing the calculations for the entire piece or disk. Other pieces were left in their prismatic form. 



