THE FEATHERS. 
83 
the case of two species of Partridges, called the 
Wood and Pock Partridge of North America, which, 
in winter, burrow underneath the snow, a still 
warmer covering is provided, the growth of feathers 
being actually doubled; so that they have nearly 
twice as warm a coat, when they most require it, 
as they had during summer, when it was unne- 
cessary. 
