THE CONQUEST OF NATURE 



The law of the inclined plane is that in order to 

 establish equilibrium between two weights, the one 

 must be to the other as the height of the inclined plane 

 is to its length. The steeper the inclined plane, there- 

 fore, the less will be the gain in power; a mechanical 

 principle which familiar experience or the simplest 

 experiment will readily corroborate. 



In its elemental form the inclined plane is not used 

 very largely in modern machinery, but its modified 

 form of the wedge and the screw have more utility. 

 The screw, indeed, which is obviously an inclined 

 plane adjusted spirally about a cylinder or a cone, is 

 familiar to everyone, and is constantly utilized in ap- 

 plying power. 



The crane or derrick furnishes a familiar but relatively 

 elaborate illustration of a mechanism for the trans- 

 mission of power, in which all the various devices 

 hitherto referred to are combined, without the intro- 

 duction of any new principle. 



Derricks have been employed from a very early day. 

 The battering-rams of the ancient Egyptians and 

 Babylonians, for example, were virtually derricks; and 

 no doubt the same people used the device in raising 

 stones to build their temples and city walls, and in 

 putting into position such massive sculptures as the 

 obelisks of Egypt and the monster graven bulls and 

 lions of Nineveh and Babylon. 



The modern derrick, made of steel, and operated 

 by steam or electricity, capable of lifting tons, yet 

 absolutely obedient to the hand of the engineer, is a 

 really wonderful piece of mechanism. A steam-scoop, 



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