120 THE BEASON WHY. 



' Such knowledge is too wonderful for me ; it is high, I cannot attain unto it."- 



PSAiM CXXXIX. 



At one extremity of the landscape, viewed through the hole in the card, there 

 may be a forest of trees ; in the distance there may be hills bathed in golden 

 light, and overhung with glittering clouds; in the mid-distance there maybe 

 a river winding its course along, as though it loved the earth through which it 

 ran, and wished, by wandering to and fro, to refresh the thirsty soil ; in the 

 foreground may be a church, covered by a million ivy leaves ; and grouping 

 towards the sacred edifice may be hundreds of intending worshippers, old and 

 young, rich and poor ; flowers may adorn the path-ways, and butterflies spangle 

 the air with their beauties : yet every one of those objects the forest, the hills, 

 the clouds, the river, the church, the ivy, the people, the flowers, the butterflies 

 must have sent rays of light, which found their way through the little hole in 

 the card, and entered to paint the picture upon the curtain of the eye. 



This is one of the most striking instances that can be afforded of the wonderful 

 properties of l$ght, and of the infinitude of those luminous rays that attend 

 the majestic rising of the sun. Not only does light fly from the grand " ruler of 

 the day " with a velocity which is a million and a half times greater than the 

 speed of a cannon-ball, but it darts from every reflecting surface with a like 

 velocity, and reaches the tender structure of the eye so gently that, as it falls 

 upon the little curtain of nerves which is there spread to receive it, it imparts 

 the most pleasing sensations, and tells its story of the outer world with a 

 minuteness of detail, and a holiness of truth. Philosophers once sought to weigh 

 the sunbeam ; they constructed a most delicate balance, and suddenly let in 

 upon it a beam of light ; the lever of the balance was so delicately hung that tho 

 fluttering of a fly would have disturbed it. Everything prepared, the grave 

 men took thdr places, and with keen eyes watched the result. Tho sunbeam 

 that was to decide the experiment had left the sun eight minutes prior to pass 

 the ordeal. It had flown through ninety-flve millions of miles of space in that 

 short measure of time, and it shot upon the balance with unabated velocity : 

 but the lever moved not, and the philosophers were mute. 



CHAPTER XXV. 



518. Why, wlien we move before a mirror, does the image 

 draw near to the reflecting surface as we draiv near to it, and 

 retire when we retire ? 



Because the lines and angles of reflection are always equal to the 

 lines and angles of incidence. 



519. What is tlie line of incidence ? 



If a person stands in a direct line before a mirror, the line 

 through which the light travels from him to the mirror is the lint 

 of incidence. 



Incidence falling on. 



