TESTS OF THE STRENGTH OF SILK FIBRES. 69 



Here, as before, we have given the actual measurements taken, the 

 strains being stated in grams and the stretch in millimeters and per 

 cents. In the recapitulation we have prepared a statement showing 

 the averages of all the measurements taken with cadi sample respect- 

 ively, as well as the highest and lowest results obtained in each, the 

 strain in each case being reduced to grains and the stretch to per cents 

 of the length. This will make the figures more intelligible to all who 

 may be interested in them, and will render a comparison much more i 

 In the lower lines we find a statement showing the number of measure 

 ments found above or below the average, as the case may be, for each 

 sample. 



In explaining the method of measuring the fineness reference has 

 been made to the peculiar structure of the fibre, resulting from the 

 mode of its production. This structure was decidedly marked in " dry "' 

 No. V. Here very many of the fibres were split either before tin- test 

 or became split by the strain or at the instant of rupture. We find 

 upon comparison of the results obtained in the tests of the split fibres 

 iu tests of whole fibres from the same cocoons that the latter are very 

 considerably stronger than the former, though as regards the percent- 

 age of stretch there appears to be no very material difference between 

 the two. And another peculiarity in the relations of the two is that the 

 strength of the whole fibre appears from the averages to be about double 

 that of the split fibres. Let us bring these averages together for more 

 ready comparison. It will suffice to express the strain as grams : 





Split. 

 grams. 



Whole, 

 grams. 



V (dry yellow) 



' • 4. -J> 



6.32 

 6.29 



V i drv white) 



3. 85 







On the other hand it may be mentioned that the uniformity in the 

 strength of the fibres as regards the strain they are able to bear pre- 

 vious to rupture, as represented in the number of measurements found 

 above and below the averages respectively, appears to be greater in the 

 split fibres. The most important difference appears therefore to be in 

 the strain representing the strength of the fibre, showing the impor- 

 tance of the more complete cementation of the fibres together as they 

 issue from the spinnerets of the worms ; and we may also learn from this 

 something of the importance of maintaining the healthy and vigorous 

 condition of the worms during their development, and more especially 

 during the period when they are spinning their cocoons. The vigor 

 and activity of the insects at the time may be very materially stimu- 

 lated by careful regulation of the temperature, ventilation, and light, 

 and not only the value of the fibre with this regard, but the condition 

 and appearance of the cocoon, upon which its market value largely 

 depends, may be modified by these relations. In this rather critical 



