TIMBER PHYSICS — EARLIER WORK. 381 



(c) Classification of woods according to physico-technical properties, i. e., such physical properties as determine 

 their application in the arts. 

 III. — Cfbmical properties, i. e., properties based on atomic (chemical) constitution, 

 (a) General chemical analysis of wood (qualitative and quantitative). 



Here would he discussed the chemical constitution of different woods and different parts of trees and 

 their changes due to physiological processes, age, conditions of growth, etc. 

 (&) Carbohydrates of the wood. 



Here would he more specially discussed cellulose and lignin, cork formations, organic contents and their 

 changes, and such properties as predicate the fuel value of woods, their manufacture into charcoal, their 

 food value, pulping qualities, etc. 



(c) Extractive materials. 



A knowledge of these underlies the application of wood in the manufacture of tan extracts, resin, and 

 turpentine, tar, gas, alcohol, acids, vanillin, etc. 



(d) Antiseptic materials. 



A knowledge of those chemical properties which predicate durability and underlie processes of increasing 

 the same. 



(e) Mineral constituents. 



A knowledge of these in particular will establish the relation of wood growth to mineral constituents 

 of the soil and also serve as basis for certain technical uses (potash). 

 IV.— Mechanical properties, i. e., properties based on elastic conditions exhibited by the aggregate mass under 

 influence of exterior (mechanical) forces. 



(a) Form changes without destruction of cohesion, commonly called elasticity, flexibility, toughness. 



(b) Form changes with destruction of cohesion, commonly called strength (tensile, compressive, torsional, shearing), 

 cleavabihty, hardness. 



V.— Technical properties, i. e., properties in combination. 



Here would be considered the woods with reference to their technical use, their application in the arts, 

 which is invariably based upon a combination of several physical or mechanical properties. 

 VI.— Diseases and faults. 



Here would be treated the changes in structure and properties from the normal to abnormal conditions, 

 due to influences acting upon the tree during its life or upon the timber during its use. 

 VII.— Relation of properties to each other. 



Here would be discussed the connection which may be established between structure, physical, chemical, 



and mechanical properties, and also between these and the conditions of growth under which the material 



was produced. The philosophy of the entire preceding knowledge would here be brought together. 



To contribute toward this important branch of human knowledge and to help in the building of its foundation, 



the work undertaken by the Division of Forestry described in this bulletin was designed by the writer j and, in 



order to build with a knowledge of what has been done before on this structure, a brief review of the progress in 



the development of timber physics seemed advisable. 



This historical review is then given. From this we deem it appropriate to quote the portion 

 which refers to efforts in the United States up to the time of the writing to establish data 

 regarding the mechanical properties of our timber : 



AMERICAN WORK. 



While it may be possible to work out the general laws of relation between physical and mechanical properties 

 on mateiial of European origin, for practical purposes we can not rely upon any other data than those ascertained 

 from American timbeis, and so far as dependence of quality on conditions of growth are concerned this truth is just 

 as patent. Although in the United States probably more timber has been and is being used than in any other 

 country, but little work has been done in the domain of timber physics. 



Among the earliest American experiments falling in the domain of timber physics may be cited those of 

 Marcus Bull to determine "the comparative quantities of heat evolved in the combustion of the principal varieties 

 of wood and coal used in the United States for fuel," made in the years 1823 to 1825 and published in 1826. Here 

 the experiments of Lavoisier, Crawford and Dalton, and Count Rumford on similar lines are discussed and followed 

 by an able series of experiments and discussion on American woods and coals. 



The only comprehensive work in timber physics ever undertaken on American timbers is that of Mr. T. P. 

 Sharpies, in connection with the Tenth Census, and published in 1884, Vol. IX, on the Forests of North America. 

 Comprehensiveness, however, has been sought rather in trying to bring under examination all the arborescent species 

 than in furnishing fuller data of practical applicability on those from which the bulk of our useful material is 

 derived. "The results obtained," the author says, "are highly suggestive; they must not, however, be considered 

 conclusive, but rather valuable as indicating what lines of research should be followed in a more thorough study of 

 this subject." 



Not less than 412 species were examined in over 1,200 specimens. The results are given in five tables, besides 

 four comparative tables of range, relative values, averages, etc. The specimens were taken " in most cases from 

 the butt cut and free from sap and knots ; " the locality and soil from which the tree came are given in most cases, 

 and in some its diameter and layers of heart and sapwood; determinations were made of specific gravity, mineral 

 ash per cent, and from these data fuel values were calculated. 



