Another great invention of humankind that has a huge impact on our societies is compass and we will talk about it in this section. This section consists of four subsections: introduction, history of compass, impact of compass on society, and conclusion.
1)What is a compass?
A compass is an instrument, which displays the direction of the horizontal component of the Earth's magnetic field at the point of observation, by a freely suspended magnetic element. A compass usually has these components:
The compass card (figure 1), engraved around its edge in degrees or points;
The magnetic assembly on which the card is mounted;
The pivot on which the magnetic assembly is poised;
The compass bowl enclosing the card, magnetic assembly, and pivot;
A lubber's point normally provided to define the compass heading.
2)Different types of compasses:
A.Simple compass (Dry-card compass)
A simple compass is a magnetized needle mounted on a pivot so that it can turn freely.
In this kind of compass the magnet and card assembly is not immersed in liquid and reliance are made on the air resistance to provide damping for the system. The needle aligns itself with the earth's magnetic field and points toward magnetic north. Simple compasses suffer from the weight limitation in loading the pivot, and therefore the magnet and card assembly is light and the magnets comparatively weak, also because of air's low degree of damping the compass is lively. On the other hand, the construction and replacement of the card and pivot are simple. , 
B.Marine compass (Liquid compass)
A marine compass (Figure 2) is a compass that is used aboard naval vessels. In this model the compass card is the moving part instead of the needle. This disk-shaped card is mounted on a jewelled pivot and small magnets are...