I am far from any intention to limit curiosity, or confine the labours of learning to arts of immediate and necessary use. It is only from the various essays of experimental industry, and the vague excursions of mind set upon discovery, that any advancement of knowledge can be expected; and though many must be disappointed in their labours, yet they are not to be charged with having spent their time in vain; their example contributed to inspire emulation, and their miscarriage taught others the way to success.