Corrosion of ferrous metals is known as rusting. Rusting of cast iron is less and rusting of wrought iron is medium while that of steel is found to be much more. Enamelling, coal tarring and galvanising are some of methods used to prevent corrosion.

Melting cast iron with wrought iron scrap results in formation of toughened cast iron. Mottled cast iron is an intermediate between white cast iron and grey cast iron.

Pig iron is crude impure iron extracted from ores of iron. Pig iron is one of basic materials used in manufacturing of steel, wrought iron as well as cast iron.

Dynamite is an explosive used in blasting process. It is very strong and can be used for quarrying under water as well. It does not need hard tamping. It is much costlier than blasting powder.

Dolerite is an example of a hypabyssal rock. Hypabyssal rocks are types of igneous rocks which are formed due to colling of magma at comparatively shallow depth from surface of earth.

Air conditioning systems are classified into two categories. These are direct expansion systems and chilled water systems. Room air conditioners and packaged units are examples of direct expansion systems.

According to physical classification, rocks are divided into three types. These are stratified rocks, unstratified rocks and foliated rocks. Physical classification of rocks is based on ir general structure. Calcareous rock is a type of rock based on chemical classification.

The amount of heat flow through a unit area of material of unit thickness in one hour, when temperature difference is maintained at 1°C is known as rmal conductivity. It is denoted by k. Its units are W/(mK).

Toughness of stone is said to be high if value of toughness index exceeds 19. If it is below 13, n stone is not tough and if it is between 13 and 19, n stone is moderately tough.

Presence of moisture in rmal insulating material decreases rmal insulation while presence of air spaces increases rmal insulation. The choice of rmal insulating material depends on various factors like cost of material, area to be covered, coat of heating or cooling, etc.