CHAPTER IX. 
PHYSICAL PROPERTIES OF REELED SILK. 
Certain physical properties are of great importance in determining 
the commercial value of reeled silk. They are its cleanliness, already 
mentioned ; ifs mean size; the irregularities in its size; its ductility, or, 
as it is wrongfully but universally called, its elasticity ; its tenacity, 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 éprouvette, and made into a little skein termed an 
échevette. This échevette 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 476 meters (400 old French ells) and a small weight called the denier. 
One dram silk in America is equivalent to a thread of 174 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 échevettes per sample skein. The 
difficulty 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- 
pound filaments are combined to make a commercial thread the matter 
becomes still more difficult. Mr. E. W. Serrell, jr., of New York, has, 
however, overcome these obstacles by relying on another property 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 now be described. The mode of testing with this 
machine is as follows: The end of the thread is brought from the reel 
or bobbin on which it is wound, around a drum (Fig. 30 A), thence over 
Fic, 30.—The principle of the Serigraph (original), 
