198 



MESSES. A. M. WORTHINGTON AND K. S. COLE 



that such figures as 2, and 3, and 4 of Series XXVII. were only obtained after the 

 glycerine had stood long enough for the exposed surface to absorb a film of water 

 from the air. Thus, if the glycerine was freshly stirred, Series XXVIII. was invariably 

 obtained, but if it stood for twelve hours exposed to the air of the laboratory 

 the splash was that of Series XXVII. We found that the gain of weight was about 

 O'Ol gramme per sq. centim. of exposed surface in twenty-four hours, so that 

 the water absorbed in twelve hours would, if it remained on the surface, form 

 a layer about -^ of a millim. thick. Using a fall of 204 centims., we found by naked 

 eye observation that the water absorbed in six hours did not suffice to change the 

 splash, while that absorbed in twelve hours always sufficed. These observations throw 

 a striking light on the determining importance of the initial motion. It should be 

 mentioned that in Series XXVII. the temperature of the glycerine was 15 C., and in 

 Series XXVIII. was 12 C., except in the last figure, when the fall was 100 centims. 

 and the temperature 22. 



Further experiments with viscous liquids are very desirable, as they may enable us 

 to pass by gradual transition to phenomena which at first sight may appear to be far 

 removed. For if any one will compare with fig. 2 of Series XXVII. , the accompany- 

 ing photograph of the permanent record left of the splash which a steel projectile 

 makes on entering a hard steel armour plate on the entering side, he will find it 

 difficult to resist the belief that the plate has behaved like a liquid. Yet even the 



Fig. 5. 



whole kinetic energy at disposal in such an impact would not suffice to raise the 

 projectile itself through more than a few hundred degrees Fahrenheit, still less to 

 melt at the same instant any appreciable quantity of metal, and we are therefore 

 driven to the conclusion that under the enormous pressure due to the impact the 

 physical properties of the material of the plate have been so far altered as to change 

 entirely the conditions of liquefaction, 



