AMI KK'AN FoRKM 1'KI 



the usual tests l>y which the strength of woods is determined. Reduced 

 to everyday language that means that 12,158 pounds would just break 

 a white elm stick, 2 5 inches square, and resting on supports twelve inchc- 

 apart. That is the meaning of "breaking strength," or "modulus of 

 rupture," as the term is used in engineering text books relating to woods. 

 The following figures for the breaking strength of other elms make 

 comparisons with white elm easy: Cedar elm 11,000; wing elm 11,162; 

 slippery elm r-V'vli*; cork elm (often called rock elm) 15,172. It is 

 shown that two elms are stronger and two weaker than white elm. This 

 wood rates very little below white oak in strength. 



The different species of elms vary considerably in stiffness, or the 

 ability to spring back when bent. This factor is expressed by engineers 

 in high figures, is purely technical, and is based on a wood's ability to 

 stretch and regain its former position. The only service which the 

 figures can render to the layman is to furnish a basis for comparing one 

 wood with another. The stiffer a wood, the greater its resistance to an 

 effort to stretch it lengthwise. White elm's measure of stiffness 

 (modulus of elasticity) is 1,070,000 pounds per square inch; wing elm 

 853,000; cedar elm 981,000; slippery elm 1,318,000; cork elm 1,512,000. 

 It is shown here, as was shown in the figures representing the strength of 

 the elms, that two species rate above and two below white elm in 

 stiffness. 



White elm is known by several names. The color of the bark is 

 responsible for the name gray elm among lumbermen and woodworkers 

 of the Lake States. American elm is a translation of its botanical name, 

 and is neither descriptive nor definitive, because there are other elms as 

 truly American as this one. White elm distinguishes its wood from the 

 redder wood of slippery elm, but it would often be difficult if not im- 

 possible to identify the elms, or any one of them, by the color of the 

 wood alone. Some persons who call this elm white doubtless refer to the 

 color of the bark, as is the case with those who speak of it as gray elm. 

 It is known as water elm in several states, but that name is applied 

 indiscriminately to any elm that frequents river banks, as most of them 

 do in some part of their range. It is called rock elm when it is found on 

 stony uplands, and swamp elm on low wet ground. In some parts of the 

 Appalachian mountain ranges it is called astringent elm to distinguish 

 it from slippery elm. 



White elm surpasses the others in extent of range. Its northern 

 boundary stretches from Newfoundland, across Canada to the eastern 

 base of the Rocky Mountains, a distance of nearly 3,000 miles. It runs 

 south through the Atlantic states to Florida, a distance of 1,200 miles or 

 more. Its southwestern limit is in Texas. The area thus bounded is 



