246 
The highest value of the tensile strength obtained for glass threads 
was 3,652 kilograms per square centimeter, while the maximum for gela- 
tine threads was 3,305 kilograms per square centimeter. It is evident that 
these values cannot represent the true values or the relative values of the 
tenacity of glass and gelatine. It may be that the internal strains set up 
in the gelatine threads were such that the tensile strengths as determined 
in this experiment were always too low. Or it may be that the “skin 
effect” in glass threads gave values far beyond the tenacity of glass in a 
plate. Further experiments along this line are in progress. 
The strength of the gelatine threads was found to increase for a few 
hours after drawing, and then to decrease—especially when the thread was 
exposed for a day or 
two to a dry atmos- geoo 
phere. Impurities tend- ELEEP ETE LL ae 
ed to weaken the Be 
threads, Curve A of 
Fig. 2 showing the ten- 
sile strength of threads gece 
of ordinary glue. Curve 
B those of gelatine con- 
taining six per cent of 
potassium chlorate, and 
Curve C those of sup- go, 
posedly pure gelatine. 
Gelatine containing six 
per cent of potassium 
alum gave a curve sim- 
ilar to Curve B; that 
is, the tensile strength 
eel alee 
ie aeees 
ett ttt 
ES 
eI 
a 
|! am 
12 
ss 
ray 
of the gelatine was di- per 
minished by the salt. S46 
Still it must be greater 
GEE 
EARSEG 
26 
glass about six per cent Ea y 
of some easily crystal- 
than the tenacity of the 
B a: 
; Bix. 
g 
q 
glass, for in chipping o OE AG Ue Oe wa 
lizable salt is mixed with the glue in order to produce the peculiar fern- 
