Fire-irons which have rested in an upright position in a room during the summer months are often highly magnetic.
Iron bars standing erect, such as the gratings of a prison cell, or the iron railings before houses, are often magnetic.
The great iron-clad ships, which have now replaced the wooden walls of Old England, are powerfully magnetic, and therefore affect the compass by which the vessel is steered; ingenious arrangements are therefore made to correct the effect of the local attraction, so that the man-of-war may be steered correctly.
Magnetism may be made to pass through a deal board; to exhibit which, lay a needle on the smooth part above, and run a magnet along the under side, and the needle will be found to follow the course of the magnet. A magnet dipped into boiling water loses part of its magnetism, which however returns upon its cooling.
A sudden blow given to a magnet often destroys its magnetic power.
