LABORATORY TESTS ON THE DURABILITY 
OF AMERICAN WOODS— I. 
FLASK TESTS ON CONIFERS 
C. J. Humphrey 
(With Plate 183) 
Introduction 
Our present knowledge of the relative durability of American 
woods has been, for the most part, derived from service or field 
tests carried out by engineers or agriculturalists. Certain of the 
larger wood users, such as railroads, telephone and telegraph com- 
panies, have for several years past kept records on the durability 
of ties, poles and other timbers as a basis for the selection of 
durable material or for determining the expediency of applying 
wood preservatives. Similar data have been secured through the 
experimental work of the United States Forest Service and the 
Agricultural Experiment Stations. 
The conditions governing such tests can not be kept uniform or 
in any way put under control. Hence, even for a single species 
of timber, the data secured will be highly variable, depending upon 
the character of the soil, drainage, air and soil temperature, pre- 
cipitation, atmospheric humidity, and any other factors which 
may influence the growth of wood-rotting fungi. Since environ- 
mental factors offer great variations between different regions of 
the United States, we can readily see why the natural durability 
of timber in warm, humid regions, for instance, frequently falls 
short of its resistance to decay in cooler, less moist localities. 
The question of the presence or absence of certain of the more 
destructive species of fungi in a given locality also influences nat- 
ural durability. In regions long free of forests the soil may, for 
instance, be comparatively free of wood-rotting fungi. The rela- 
tive great abundance of decay-producing species and individuals 
in the tropics is one factor in the rapid deterioration of timber in 
those regions. It is but Nature’s way in maintaining the proper 
80 
