22 WONDER AND MYSTEKT. 



There was the flame perfectly formed, though pointing 

 downward, and the wick (which appeared like a slender 

 black line in the middle of it), and the top of the candle 

 (which was rendered bright for a little distance by the 

 translucency of the wax at the margin), all plainly to be 

 seen. 



John was very much pleased to find his experiment so 

 successful, and he called Lawrence to come and see it. 

 Lawrence came, and he showed John how he could vary 

 the effect by changing the distance of the lens from the 

 candle, though this made it necessary also to change the 

 distance from the lens to the screen. The nearer the can- 

 dle was to the lens on one side, the farther it was necessary 

 to place the screen on the other, in order to bring the rays 

 to a, focus, as it is called that is, to make the image dis- 

 tinct. 



John was, however, very much surprised to find that 

 there was no dark line across the picture of the candle 

 corresponding to the bar formed by the bow of the spec- 

 tacles. Lawrence told him it would be the same with any 

 opaque substance at the surface of the glass. He might 

 put a patch directly upon the glass itself, and it would not 

 show as a spot of shadow on his picture. 



John tried this experiment. He cut out a small round 

 piece of paper about as large as the section of a pea, and 

 then, wetting it to make it adhere, he put it on the glass. 

 Notwithstanding what Lawrence had told him, he could 

 not help expecting to see it produce a round black spot 

 upon the image of the candle. But it did not do so. The 

 image became somewhat less bright than before, it is true, 

 but there was no appearance upon it of any shadow, either 

 from the bar or from the paper patch. 



Lawrence explained to him how this was, and I intend 

 to repeat the explanation in a future chapter ; but now I 



