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dra'srs its suhstanre largely from the more compreheiisive fields of botany, uiokfiilar physie.s, and 

 chemistry, and on the other side it rests npoii investigations of the wood material from the point 

 of view of mechanics or djniamics. In the first direction we are led to deal with the wood material 

 as it is, its nature or appearance and condition; in the second direction we consider tlie wood 

 mateiial in relation to external mechanical forces, its behavior under stress. 



The first part is largely descriptive, concerned in examining gross and nunute structures, phys- 

 ical and chemical condrtions and properties, and ultimately- attempting to explain these by refer- 

 ring to causes and conditions ^hich produce them. This is a field for investigation and research 

 by the plant physiologist in the laboratory in connection with studies of environment in the forest. 

 The second part, which relies for its development mainly upon experiment by the engineer, deals 

 with the properties which are a natural consequence of the structure, physical condition, and chem- 

 ical composition of the wood as exhibited under the application of external mechanical forces. 

 It comprises, therefore, those studies which contenudate the wood substance, with special refer- 

 ence to the uses of man, and forms ultimately the basis for the mechanical technology of wood or 

 the methods of its use in the arts. 



The correlation of the results of these two directions of study as cause and effect is the highest 

 aim and ultimate goal, the philosophy of the science of timber physics. Timber physics, in 

 short, is to furnish all necessary knowledge of the i-ational application of wood in the arts, and at 

 the same time, by retrospection, such knowledge will enable us to produce in our forest growth 

 qiralities of given character. 



Conceived in this manner it becomes tlie pivotal science of the art of forestry, around which 

 the practice both of the consumer and producer of forest growth moves. 



The first part of oar science would require a study into gross and minute anatomy, the struc- 

 ture of the wood, form, dimensions, distribution, and arrangement of its cell elements and of groups 

 of structural parts, not only in order to distinguish the different woods, but also to furnish the 

 basis for an explanation of their physical and mechanical i)roperties. We next would class here 

 all investigations into the physical nature or properties of the wood material, which necessarily 

 also involves an investigation into the change of these properties under varying conditions and 

 influences. A third chapter would occupy itself with the chemical composition and jjroperties of 

 woods and their changes in the natural process of life, wliicli ju'edicate the fuel value and dura- 

 bility as well as the use of the wood in chemical technology. 



Although, philosophically speaking, it would hardly seem admissible to distinguish between 

 physical and mechanical properties or to speak of " mechanical " forces, for the sake of convenience 

 and practical purposes it is desirable to make the distinction and to classify all phenomena and 

 changes of nonliving bodies, or bodies without reference to life functions, into chemical, physical, 

 and jnechanical phenomena and changes. As chemical phenomena or changes, and therefore also 

 conditions or properties, we class, then, those which have reference to atomic structure; as phys- 

 ical phenomena, changes and properties, those which refer to and depend on molecular airange- 

 ment; and as mechanical (molar) changes and properties those wluch concern the masses of bodies, 

 as exhibited undei-the influence of external forces, without altering their jdiysical or chemical con- 

 stitution. 



There is no doubt that this division is somewhat forced, since not only most or all mechanical 

 (as here conceived) changes are accompanied or preceded by certain alterations of the interior 

 molecular arrangement of the mass, Init also many i)hysical phenomena or properties, like density, 

 weight, shrinkage, having reference to the mass, might be classed as mechanical; yet, if we con- 

 ceive that physical phenomena are always concerned with the "quantity of matter in molecu- 

 laf arrangement" and with the changes produced by interior forces, while the latter are concerned 

 rather with the " position of matter in molecular arrangement " and witli changes under applica- 

 tion of exterior forces, the distinction assumes a practical value. 



Our conception of these distinctions will be aided if we refer to the physical laboratory as fur- 

 nishing the evidence of physical phenomena, and to the mechanical laboratory as furnishing evi- 

 dence of mechanical ijhenomena. 



These latter, then, form the subject of our second i)r dyinuiiic jiart of timber physics, which 

 concerns itself to ascertain maiidy l)y experiment, called tests, under application of the laws of 



