174 THE FOKMS OF WATER IN 



440. The lowering of the freezing point by pressure 

 amounts to no more than one-seventieth of a degree 

 Fahrenheit for a whole atmosphere. Considering the 

 infinitesimal fraction of this pressure which is brought 

 into play in some cases of regelation, Faraday thought its 

 effect insensible. He suspended pieces of ice, and brought 

 them into contact without sensible pressure, still they 

 froze together. Professor James Thomson, however, 

 considered that even the capillary attraction exerted 

 between two such masses would be sufficient to produce 

 regelation. You may make the following experiments, 

 in further illustration of this subject : — 



441. Place a small piece of ice on water, and press it 

 underneath the surface by a second piece. The sub- 

 merged piece may be so small as to render the pressure 

 infinitesimal ; still it will freeze to the under surface of 

 the superior piece. 



442. Place two pieces of ice in a basin of warm water, 

 and allow them to come together ; they freeze together 

 when they touch. The parts surrounding the place oi 

 contact melt away, but the pieces continue for a time 

 united by a narrow bridge of ice. The bridge finally 

 melts, and the pieces for a moment are separated. But 

 capillary attraction immediately draws them together, 

 and regelation sets in once more. A new bridge is 

 formed, which in its turn is dissolved, the separated 

 pieces again closing up. A kind of pulsation is thus 

 established between the two pieces of ice. They touch, 



