OF THE SALMOmBM. 57 



corner, the object being to exclude external 

 and, therefore, hot air as much as possible. 

 The boxes containing the ova cover the 

 floor of the ice-house, fitting closely to one 

 another. Upon these are piled cubic blocks 

 of Wenham Lake ice, measuring about two 

 feet, right up to the roof of the ice-house, 

 leaving just space for another tier of boxes 

 upon the top of the ice. The entrance to 

 the ice chamber is closed by a very heavy 

 lid with bevelled edges, covered with sheet 

 lead, and made to jam tightly into the 

 opening, and, when all is complete, covered 

 with thick felt. What goes on in the ice- 

 house during the voyage may be told in a 

 few words. Nothing, of course, will prevent 

 the ice from wasting slowly away. As it 

 does so the water from it percolates through 

 the boxes — perforated to allow of this — and 

 escapes by the drains below, the upper tier 

 of boxes sinking gradually with it. Thus 

 they are always in contact with the ice. It 

 is absolutely essential that a considerable 

 quantity of ice should remain to the end of 

 the voyage, both to keep down the tempe- 



