The different kinds of motive power used to actuate cranes - manual, steam, hydraulic, electric - give a further classification.
Steam is an extremely useful motive power for all cranes that are not worked off a central power station.
Electricity as a motive power for cranes is of more recent introduction.
For overhead travellers in workshops, and for most of the cranes which fall into our second class, electricity as a motive power has already displaced nearly every other method.
It is now possible to apply motive power exactly where it is wanted, and to do so economically, so that the crane designer has a perfectly free hand in adding the various motions required by the special circumstances of each case.