OF NATURAL PHILOSOPHY. 63 



strength has hitherto defied all useful manage- 

 ment, or rather to spirits evoked by the spells of a 

 magician, manifesting a destructive and unapproach- 

 able power, which makes him but too happy to close 

 his book, and break his wand, as the price of escap- 

 ing unhurt from the storm he has raised. Such 

 powers are not yet subdued to our purposes, what- 

 ever they may hereafter be ; but, in the expansive 

 force of gases, liberated slowly and manageably from 

 chemical mixtures, we have a host of inferior, yet 

 still most powerful, energies, capable of being em- 

 ployed in a variety of useful ways, according to 

 emergencies. * 



(58.) Such are the forces which nature lends us for 

 the accomplishment of our purposes, and which it is 

 the province of practical Mechanics to teach us to 

 combine and apply in the most advantageous man- 

 ner ; without which the mere command of power 

 would amount to nothing. Practical Mechanics is, 

 in the most pre-eminent sense, a scientific art; and 

 it may be truly asserted, that almost all the great 

 combinations of modern mechanism, and many of its 

 refinements and nicer improvements, are creations of 

 pure intellect, grounding its exertion upon a mode- 

 rate number of very elementary propositions in 

 theoretical mechanics and geometry. On this head 

 we might dwell long, and find ample matter, both 



* See a very ingenious application of this kind in Mr.. Bab- 

 bage's article on Diving in the Encyc. Metrop. Others 

 will readily suggest themselves. For instance, the ballast in 

 reserve of a balloon might consist of materials capable of evolv- 

 ing great quantities of hydrogen gas in proportion to their 

 weight, should such be found. 



