3 



and comprelieiisivo, manner, such tests and examinations as wonld Inrnisli its not only witli relia1>1(> 

 data as to the range of capacity of our timbers, but also as to tlio exact relation of their pro|ierties 

 to their structure and physical condition. 



In order to establish fully for any one species the possibilities of its adaption to our use, it is 

 necessary to test a very large number of specimens. lu order to formulate laws of relation between 

 physical condition, anatomical structure, and mechanical properties, each test specimen must be 

 earefully examined. In order to establish laws of relation betweeu the i)liysical and mechanical 

 ipialities and the conditions under whicli the spe<'imfn has grown, it is necessary to perform the 

 testing and the examination on a large number of specimens of known origin. 



Almost all the investigations made in this line are deticient in one or more or all ot these points. 

 Xot only have there been few tests made on a sutlicient quantity of material to allow generaliza- 

 tion, but rarely Lave there been suHicient data furnished regarding the nature and origin of the 

 test specimens to enable us to form a judgmeut. 



Whatever laws of interrelation betweeu physical structure and mechanical properties have 

 been established or indicated, we owe almost entirely to European investigators on European tim- 

 bers. Our engineers' tables are mainly made up from European sources, and while tlie extensive 

 tables of the Tenth Census, prepared by Prof. C. E. Sharpies, give us an indiciation as to the rela- 

 tive values our of many species, they can hardly claim to I'urnish data for iiractical application; in 

 fact the author himself distinctly disclaims this. Anyhow, no attempt lias been made to find out 

 the causes of variation in properties or even to give data from which argument might proceed or 

 a relation between properties and structure might be inferred. 



It is to supply this absolute gaji in our knowledge — which causes tliousands and millions of 

 dollars of waste auuually — that the Forestry Division has entered upon a comprehensive and 

 systematic investigation which has become known under the name of "the Government timber 



tests." 



This investigation, the most comi)rehensive of the kind ever undertaken anywhere, in this 

 country or in Europe, differs from all former attempts in similar direction in this, that it starts 

 out Avith the fullest recognition of three fiicts: 



(1) That in order to establish reliable data as to mechanical properties of our timbers, it is 

 necessary to make a very large number of tests, by which the range as well as average capabili- 

 ties of the species is determined. 



(2) That in order to enable us to make the most eHicient practical application of the data thus 

 obtained it is necessary to know the physical and structural conditions of the test material and 

 bring these into relation with the best results. 



(3) That in order further to deduce laws of relation between mechanical properties and the 

 physical and structural conditions, as well as the conditions under which the material was pro- 

 duced, it is necessary to work on material the history of which is thoroughly known. 



Brieily, then, to solve the problems before us, it is necessary to make our tests on a large num- 

 ber of specimens of known origin and kiu)wn physical condition. Whih^ the tests in themselves 

 appeal at once and lirst to the engineer, inasmuch as, by their great number, they will furnish more 

 reliable data regarding the capabilities of the various timbers, the chief value and most important 

 feature of the work lie in the attempt to relate the mechanical properties to the structure of the 

 material and to the conditions under which it was produced. 



We are not only concerned to know that a stick of this si)(!cies of tree will bear a given load, 

 but we want to be able to tell why this stick of the species will bear so much and why the other 

 stick of the same species will bear only half as much; why the timb.n- grown in this locality ia 

 found generally superior to that of the same species grown in another locality, etc. 



When we have established such knowledge, then it will be possible for an engineer not only 

 to specify his timbers intelligently, but also to ins])ect them and to know whether or not they come 

 up to his spcciticatious. To be sure, we are not now quite without some knowledge regarding 

 these matters, although few users of wood seem aware of it. But not only is this knowledge 

 scanty, it is not quite certain or capable of general application, and the results and deductions 

 of one investigator may often be louiul contradicted by another or by the same authority after 



