midday
`` Call it what you like ; but that was a crumb which fell down here , my lad . You see the snow and ice over yonder ? '' `` Yes . '' `` Well , of course that means that there is constant freezing going on there , except when the sun is blazing down at midday . '' `` Yes , I understand that , '' said Saxe . `` Well , the rock gets its veins charged with water from the melting of the snow in the daytime , and at night it freezes again ; the water expands in freezing , and splits the rock away , but it does not slip , because it is kept in position by the ice . By-and-by , on an extra hot day , that ice melts , and , there being nothing to support it , the mass of rock falls , and drives more with it , perhaps , and the whole comes thundering down . ''