( 285 ) 
less. No secular variation is known. From these data it appears 
that the temperature to which the vessel was exposed for 22 centu- 
ries cannot, for any prolonged period, have been higher than 20°C. 
6. In the last communication on the enantiotropy of tin, the 
velocity of the change 
white tin — grey tin 
was determined at different temperatures. It was found that the 
change 
grey tin — white tin 
(above + 20° C.) in absence of a solution of pink salt took place 
very slowly, so that it appeared possible to study the velocity also 
above the transition point. 
In all systems investigated up to the present, which have a 
transition temperature, the change takes place so rapidly above this 
temperature that determinations of the velocity are impossible. 
I filled a dilatometer with about 30 grams of grey tin and added 
water to serve as the measuring liquid. In this way the pure phe- 
nomenon may be studied. 
The dilatometer was placed in a thermostat the temperature of 
which could be maintained constant within 0.03° by means of an 
electric regulator. The position of the liquid was read from time to 
time on the porcelain millimeter scale placed behind the capillary ; 
the corresponding times were measured by a chronometer to 1/5 sec. 
In order to be able to regard the mass undergoing the change 
as the same at all temperatures, a very small quantity of tin was 
allowed to change at each temperature. 
Temperature ‘Time (in minutes) Fall of the level of the Fall per hour. 
liquid in mm. 
30°,0 60 7,2 7,2 
30°,0 60 7,25 7,25 
31°,0 40 13,0 19,50 
32°,0 51 30,0 35,0 
33°,0 6 10,75 107,5 ) 
33°,0 6 10,5 iki ee ah 
34°,0 6 17 Be.) 
34°,0 6 19 igo ye 
35°,0 3 25 500 
35°,0 51/5 44 500 
