At some of our colleges and inns of court, the serving of the boar's head on a silver platter on Christmas-day is a custom still followed; and till very lately, a bore's head was competed for at Christmas time by the young men of a rural parish in Essex.

The density of the cloud is proportionate to the number of the particles; hence the fact that the steam issuing from the safety-valve or the chimney of a locomotive forms a dense white cloud, shows that the air is really full of dust particles, most of which are microscopic but none the less serving as centres of condensation for the vapour.