When loaded by shovel the car is made low to economize labour.
This type of structure, which is extremely various in its details, is found especially, as we should expect, in plants which have to economize their water supply.
Sometimes also a viaduct consisting of a series of arches is preferred to an embankment when the line has to be taken over a piece of fiat alluvial plain, or when it is desired to economize space and to carry the line at a sufficient height to clear the streets, as in the case of various railways entering London and other large towns.
One of the advantages of electric trains on the multiple control system is that they economize terminal accommodation, because they can be driven from either end indifferently, and therefore avoid the necessity for tracks by which engines can change from one end of the train to the other.
Although spherical forms can be obtained without the use of moulds, moulds are now largely used for even the simplest kinds of tableware in order to economize time and skilled labour.