TESTS OF THE STRENGTH OF SILK FIBRES. 63 



instrument is so constructed that the strain to which the fibre is sub- 

 jected to break it, and the stretch it sustains previous To rapture, are 

 simultaneously taken and recorded, and we have, therefore, to present 



iu this connection two sets of results. 



In making these tests the following method was employed : In the 

 first place the cocoons were cut open and their layers separated, or they 



were submitted to the action of hot water and the fibres wound off upon 

 pieces of card-board, each process furnishing the "dry" and -wcr" 

 specimens respectively described in a preceding paragraph. From the 

 loose fibre thus obtained Sections of suitable length were taken at ran- 

 dom for the individual tests, the "tcet" specimens having been previ- 

 ously thoroughly dried. The two clamps holding the fibres in the in- 

 strument during the tests were carefully set at a distance of 20 milli- 

 meters apart, so that this distance represents the length of the fibre 

 submitted to the strain. Experiments with woolen fibres showed this 

 distance to give the most uniform and satisfactory results, and is, there- 

 fore, accepted as a standard for all our work. Although no special ex- 

 periments were made with this regard on the silk examined, there is 

 little doubt that it would be found equally satisfactory. 



In this part of the examination as in the measurements of fineness, 

 we have adopted 30 as the best number of fibres to be tested to secure a 

 satisfactory average, and as before, each separate result obtained was 

 entered upon the record to be employed in any comparisons that it may 

 appear to be desirable to name. For their more ready comparison the 

 results obtained with the "dry" and u wet 7f specimens, respectively, are 

 placed side by side. The following table contains the results we have 

 obtained : 



