Aids to Microscopic Inquiry. 49 



it appears to be an elastic body, as, when, viewed under high 

 magnification, a wave-motion may be traced throughout its 

 length. Let the reader experiment with two sticks, each a 

 yard long, one stiff, the other elastic, and he will find how much 

 easier it is to give the elastic one a great velocity at the extre- 

 mity furthest from his hand. The well-known instrument 

 called a " life-preserver" owes to the elasticity of its stem much 

 of the force with which its knob can be made to fall. 



There are few principles of construction employed by man 

 that are not found exemplified in objects which the microscopist 

 will be able to study. Arched forms are abundant in the 

 animal and vegetable world. The Melicerta,* one of our most 

 interesting rotifers, makes her own bricks, and builds a round 

 tower. The corrugated or fluted arrangement is found in many 

 stems of plants, and in one of the moon-shaped desmids; while 

 the shells of many foraminifera display the advantages of ribs in 

 giving strength. 



The so-called teeth of the Prorodon teres, and certain other 

 infusoria, appear, when examined with sufficient power and good 

 illumination, to be merely a corrugated arrangement of some 

 stiff material, the precise use of which has not been ascertained. 



The action of the so-called mechanical powers should always 

 be noticed in living objects, many of which possess remarkable 

 tools. By employing levers two different purposes may be 

 served. If a crowbar is put under a heavy stone, and rested on 

 a fulcrum near it, when the end furthest from the stone has de- 

 scended several feet, the stone may be raised an inch or two. 

 In this case, by moving the hand of the man who holds the 

 crowbar through a large space, the weight to be lifted is moved 

 through a small one, and the gain in power is proportioned to 

 the loss in time. That is to say, the hand moving with a certain 

 velocity, could traverse the small space through which the stone 

 moves much quicker than it does traverse the larger space 

 through which it passes, and carries with it the extremity of 

 the lever's long arm. Here the lever is made the means of 

 lifting a weight greater than the same force could have moved 

 had it been directly applied. There is a loss of time, and a 

 gain of power. But when a boatman makes a fulcrum of one 

 of his rowlocks, and by moving his hand and one end of the 

 oar through a small space, causes the other end of the oar to 

 move through a much larger space in the same time, the force 

 with which the extremity of the oar strikes the water would 

 not move a weight equal to that which the hand could 

 have moved if directly exerted upon it. In the first case, the 

 hand moved through a large space, while the short arm of the 

 lever moved through a little one ; and, in the second case, the 

 * See Marvels of Pond Life. Groombridge and Sons. 

 VOL. VI. — NO. I. E 



