236 



AMERICAN FORRSTRY 



There is another way of making wood into wearing 

 apparel. After it is reduced to pulp, as for making paper, 

 the fibers are dissolved by chemicals and the solution 

 squirted out through extremely minute holes and harden- 

 ed into delicate threads something like the strands of a 

 spider web. This is artificial silk which has become the 

 great rival of the natirral product of the silkworm. 



WOOD STRAINS 



The name "wood strains" is applied to the wooden 

 insulators used in overhead electric line construction. 

 They consist of turned pieces of hard wood enlarged in 

 the middle and at the ends. They vary in length from 

 eight inches to three feet and are from an inch to four 

 inches in diameter at the smallest part. Malleable iron 

 lugs with eyes for fastening to the guy wires are 

 swedged onto the enlarged ends so that the wood is sub- 

 jected to an endwise pull. 



Photograph by S. J. Record 



A WOOD STRAIN 



There is no danger of the wood being pulled in two, the lugs at 



the end would slip off first. 



Wood is used because in a dry condition it is a very 

 poor conductor of electricity. Maple is the principle 

 species employed for this purpose but many hard, strong, 

 easily turned woods will do. The dry pieces are thor- 

 oughly impregnated with parafine and then coated with 

 a heavy oil paint. The latter wears oflf in time but the 

 parafine alone affords fairly good protection. 



There is no danger of the wood being pulled in two 

 because wood is so much stronger in tension than in re- 

 sistance to shear. If a wood strain fails it is from some 

 other cause, more likely the pulling oflf of the lugs. 

 Porcelain and other kinds of insulators are being sub- 

 stituted on electric railroads but the trolley lines still 

 use large numbers of the wooden kinds. 



PLUGGING HOLES IN CROSSTIES 



Whenever a spike is pulled out of a crosstie the hole 

 that is left affords excellent opportunity for the entrance 

 of water carrying spores and disease germs to the interior. 

 To overcome this the holes are now commonly filled with 

 wooden plugs. These are used by the million and are 

 for the most part sawed by special machines from slabs 

 and scraps from the mills and shops. Some railroads make 

 some of their own plugs in the shops or employ the spare 

 time of the section men in splitting them out of old ties. 

 The common size is about four-and-a-half inches long, 

 five-eighths of an inch square in cross section and with 

 one end wedge-shaped like a spike. For untreated ties 

 white oak or other durable wood is preferred for plugs. 

 Any wood can be used where the ties are treated since 

 the plugs are placed in gunny sacks and impregnated with 

 the preservative along with the ties. 



PINE STRAW ROADS 



In certain parts of Florida, particularly in the lime- 

 sink and lake regions, the sand is very deep and there 

 is no clay available to make the roads firm. In the open 

 pine woods, however, are large quantities of the long 

 needles or pine-straw which makes a very satisfactory 

 road material upon which autos can travel without dif- 

 ficulty. There are hundreds of miles of such roads in 

 the state. 



A TYPICAL ROAD 

 Pine straw road used mostly by automobiles going up Iron Moun- 

 tain, near Lake Wailes, Polk County, Florida. 



The straw is raked up in the woods and hauled to the 

 road where it is spread to a depDh of about a foot, 

 though it soon gets flattened down. The work is usually 

 done in early spring and costs from 40 to 60 dollars a mile. 

 One strawing will usually last for a season and sometimes 

 two. Unlike ordinary road materials this is in constant 

 danger from fire so the expression "burning up the road" 

 has a literal meaning in Florida. 



MAKING PAPER NEGATIVES AND PRINTS 

 FROM WOOD SECTIONS 



It is often desirable to have prints showing in natural 

 size the structure of woods. ' If well made they show 

 the size, number, and arrangement of pores and other 

 characteristics and for many purposes of comparison and 

 study they serve nearly as well as the wood itself. The 

 use of a camera for such purposes is not only expensive 



Photograph by S. J. Record 



AMERICAN ELM WOOD 

 Positive print. Paper negative. 



