Contrive a new machine, and every body will be interested to witness or to hear of its operation.

Develop any heretofore unknown properties of matter, or secure some new useful effect from laws which men have not hitherto employed for their purposes, and the interest of all around you will be excited to observe your results; and, especially, you will yourself take a deep and permanent pleasure in guiding and controlling the power you have thus obtained.
This is peculiarly the case with experiments upon mind, or experiments for producing effects through the medium of voluntary acts of others, making it necessary that the contriver should take into consideration the laws of mind in forming his plans.

To illustrate this by rather a childish case: I once knew a boy who was employed by his father to remove all the loose small stones, which, from the peculiar nature of the ground, had accumulated in the road before the house.

The boy was set at work by his father to take them up, and throw them over into the pasture across the way.

He soon got tired of picking up the stones one by one, and so he sat down upon the bank to try to devise some better means of accomplishing his work.