. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. CHAPTER IX. PHYSICAL PROPERTIES OF REELED SILK. Certain physical properties are of great importance in determiuing tbe commercial value of reeled silk. They are its cleanliness, already mentioned ; its mean size; the irregularities in its size; its ductility, or, as it is wrongfully but universally called, its elasticity; its tenacitj'^, and the amount of soluble gum which it contains. The mean size of a skein is determined in the following manner: One thousand yards of the thread is wound off on a reel, supplied
. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. CHAPTER IX. PHYSICAL PROPERTIES OF REELED SILK. Certain physical properties are of great importance in determiuing tbe commercial value of reeled silk. They are its cleanliness, already mentioned ; its mean size; the irregularities in its size; its ductility, or, as it is wrongfully but universally called, its elasticity; its tenacitj'^, and the amount of soluble gum which it contains. The mean size of a skein is determined in the following manner: One thousand yards of the thread is wound off on a reel, supplied with a counter called an eprouvettc, and made into a little skein termed an echevette. This echevette is then weighed and the number of sixty- fourths of a dram which it is found to equal becomes the size number of the thread. This process is called the sizing, or, colloquially, the "dramming" of silk. In Europe the same system is employed, but the units are a length of 470 meters (400 old French ells) and a small weight called the denier. One dram silk in America is equivalent to a thread of 17^ deniers in France. Until recently there has been no means of determining the irregular- ities in size existing in a silken thread, but manufacturers were content to approximate it by weighing four echevettes per sample skein. The difliculty in making this determination is owing to the fact that the thread is not round, but flattened, being, in fact, in its simple state, two filaments joined into one, and when several of these naturally com- j)Ound filaments are combined to make a commercial thread the matter becomes still more difticult. Mr. E. W. Serrell, jr., of New York, has, however, overcome these obstacles by relying on another i^roperty of a silk filament, which is, that the distance which a given length will stretch under a given tension is inversely proportionate to the mean cross-section of this length. This is the underlying principle of his serigraph, which will
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