Lecture

 1 II|      shadow from this little screen B F (merely a square piece
 2 II|  place it close to the large screen, just shadows as much of
 3 II|     between the lamp and the screen; now look at the size of
 4 II|  distance, and, if I put the screen at one-third of the distance
 5 II|      the shadow on the large screen would be nine times the
 6 II|  size. Again, if I hold this screen here, at B F, a certain
 7 II|    off from the part of this screen, B D, now in shadow; moreover,
 8 II|   see that if I put a single screen here, at G, by the side
 9 II| square of the distance. This screen E is the brightest because
10 II|       but it is bent to this screen, C, and how much more beautiful
11 II|    prismatic spectrum on the screen]. This ray of light is bent
12 II|     once more bent on to the screen, and you see how wonderfully
13 II|     adjust it as to make the screen upon which it is shining
14 II|     get through. You see the screen remains dark. The glass,
15 II| light to pass through to the screen, and how, as Dr. Tyndall
16 II|     course of the light, the screen still remains dark. Now
17 II|   effect that has. [Upon the screen two white dots gradually
18 II|    light passes through; the screen remains quite dark; but