We give a summary of" our results in the following table ^). 



27o gelatin-gljcerin solution cooled to 16° after heating to 70° 

 Readings after hr 1 hr 2 lirs 3 lirs 12 hrs 



Consistence fluid viscous nearly solid solid solid 



Intensity 0,25 1 1,4 1,4 2,8 



The conversion from sol to gel is not sudden. 



In another experiment the initial intensity of the TvNDALL-phe- 

 nomenon at the temperatui-e of the experiment was greater than 

 when the solution reached the equilibriinn, determined by this tem- 

 perature, so that, as the test proceeds a reduction of the intei:sitj 

 is to be looked for. The experiment was performed with a 1 "/o 

 solution that had been kept at room-tem[)erature for some time and 

 had subsequently been warmed to 50°. At tliis temperature the solution 

 luas fluid always. At intervals of 24 hrs three determinations were 

 made, demonstrating a slow and slight diminution of the intensity 

 of the light. 



1% gelatin-glycerin after JO days at 16° — 18', warmed to 25°. 



Readings afier : 1 day 2 days 3 days 



Consistence : fl. fl. fl. 



Intensity : 5,6 4 4 



After heating to 70° the intensity was rapidly reduced to 0,5 

 and then remained constant. Experiments such as these can be 

 repeated at will on the selfsame liquid. The results will ever be the 

 same. They are in keeping ^vith the abo\'e survey, so that we are 

 iustified in concluding that the intensity of the TYNUALL-phenomenon 

 always approximates its equilibrium value and that in that state it 

 is a function of the temperature. 



Hereafter we were eager to know, whether the changes of the 

 Tyndall-couc occur only when the solution passes from sol to gel 

 or whether they are not dependent on this conversion. To ascertain 

 this a series of experiments were carried out with a 17o solution, 

 that had been heated beforehand to 70°. They were continued for 

 12 days, in which time the viscosity w^as highly increased, but a 

 conversion to gel was out of the question. At first an exposure was 

 made every 24 hrs, later on every 2 X 24 hrs. It appeared that 

 after 12 days no equilibrium had been established; from the 1^*^ to 

 the 8^'' exposure (on the 12^" day) a set of negatives was obtained, 



1) Tlie values recorded apply to llie most intense portions of tlie cone. They 

 are calculated from ratios for whicli the unit svas arbitrary. 



