SCIENCE AND POETRY. 



When the observer, looking over the gunwale of a boat, is 

 within two feet, for example, of the water, the image produced by 

 the reflected rays is only four feet distant. The intensity of the 

 light is therefore greater, other things being the same, than in 

 the former case, in tile proportion of the square of 4 to the square 

 of 24, or what is the same, in the proportion of 36 to 1. 



5. But besides this, there is another circumstance to be taken 

 into account. The rays of the pencils which, diverging from the 

 person of the observer, are reflected by the water and received by 

 the eye, have a greater obliquity than in the former case, in the 

 same proportion nearly as that in which the distance of the observer 

 from the surface of the water is diminished, and consequently 

 according to the results given in the above table, a much greater 

 proportion of these rays will be reflected. On both these accounts 

 the image, which was imperceptible from the bulwark of the 

 vessel, is often perceptible from the gunwale of the boat. 



In all such observations, however, there are numerous modify- 

 ing conditions which will vary the result in different cases. Thus, 

 if the water be clear and transparent, and the bottom strongly 

 illuminated, the light reflected from it will often predominate so 

 much over the rays which produce the image to the observer, that 

 this image will cease to be perceptible. 



6. We have tried some simple experiments on this subject, the 

 results of which are instructive, and which may be easily repeated 

 by any of our readers. 



Fill a basin with water, and place it near an open window, look 

 down from a height of five feet vertically above the surface of the 

 water. You will not perceive any trace of your own image in the 

 water. Descend gradually towards the surface, and when your 

 face is at about four feet above it, the faintest conceivable image 

 of it will begin to be perceived. On approaching still closer, the 

 image will be a little, but a very little, more perceptible, but even 

 at the least distances the reflection will be so faint that it can only 

 be perceived by concentrating the attention upon it. 



Let the basin be now surrounded with a sheet or any other 

 expedient, by which the light falling from the window upon the 

 water shall be excluded, but so that your face being above the 

 edge of the sheet shall be still illuminated. You will then per- 

 ceive your reflected image with tolerable distinctness in the water, 

 even at a distance of four or five feet above its surface, and this 

 distinctness will be increased as the distance of your face above 

 the surface of the water is diminished. 



7. The explanation of these effects is obvious. When the water 

 in the basin is exposed to the light of the window, the quantity 

 of the light reflected from the bottom of the basin to the eye of 



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