14 NATURE'S TEACHINGS. 



and therefore couid not be the fulcrum. This objection, how- 

 ever, was easily refuted by taking a boat up a narrow creek, 

 and rowing with the oar-blades resting on the shore, and not in 

 the water. 



Now, the swimming legs of the water -boatman are exact 

 analogues of the oars of a human rower. The internal muscles 

 at the juncture of the leg with the body supply the place of the 

 rower's arms, the leg itself takes the office of the oar, and the 



OAR OF BOAT. 



WATER-BOATMAN ROWING ITSELF. 



OARSMAN ROWING. 



body of the insect is the weight to be moved, and the water 

 supplies the fulcrum. Even the broad blade at the end of the 

 oar is anticipated by the fringe of bristles at the end of the leg, 

 and its sharpened edge by the shape of the insect's limb. 



Besides these resemblances, there is another which is worthy 

 of notice. All rowers know that one of their first lessons is to 

 " feather " their oars, i.e. to turn the blade edgewise as soon 

 as it leaves the water. Nothing looks more awkward than 

 for a boatman to row without feathering. (We all must 

 remember the eulogy on the " Jolly Young Waterman," who 

 " feathered his oars with skill and dexterity.") In the first 

 place, he must lift his oar very high out of the water, and, in 

 the second, he will be impeded by any wind that happens to 

 come against the blades. 



The Water-boatman, however, does not lift its legs out of the 

 water after every stroke, as a human boatman does, and there- 

 fore it has no need to feather in the same way. But there is 

 even greater need for a feathering of some kind in the insect's 

 leg, on account of the greater resistance offered by water than 

 by air, and this feathering is effected by the arrangement of the 

 blade-bristles, which spread themselves against the water as 

 the stroke is made, and collapse afterwards, so as to give as 

 little resistance as possible when the stroke is completed. 



