292 



not a very comfortable one, although I have often followed it 

 on a windy day when the surface was too ruffled to permit of 

 vision in any other way. 



Still, there is an instrument by which it is possible to counter- 

 act the ruffle of the surface, and to see objects with tolerable 

 plainness. This is called the Water Telescope, and it is of very 

 simple construction. Like the ordinary telescope, it consists of 

 a tube, but, instead of the convex and concave lenses of that 

 instrument, it has only a single glass at one end, and that 

 glass is perfectly plane. 



When used, the eye is applied to the open end, and the glazed 

 end lowered into the water. The sight is then undisturbed by 



WHIRLWIG-BBETLE. WATER TELESCOPE. 



the ripple, and the effect is the same as if the eyes themselves 

 were lowered beneath the surface. 



It is much used in looking for shells, sea-urchins, and other 

 creatures which live in the bed of the sea. 



IN the insect world we have an example of a natural Water 

 Telescope. I do not say that the inventor of the Water 

 Telescope took his idea from the insect, but the reader will see 

 that he might very well have done so. 



There are sundry little beetles popularly called Whirlwigs or 

 Whirligigs, and scientifically known by the name of Gyrinus. 

 All these names allude to the insect's habit of whirling about on 

 the surface of the water, with a movement which seems cease- 

 less and untiring. Allusion has already been made to the 

 Whirlwigs on page 22. 



