AS TO SOUADNESS. 6i 



We have, then, two arches crossing each other at right 

 angles, which have the same centre of weight. The centre 

 or focus of weight is at the coffin-joint, — please remember 

 that. After passing this joint the weight radiates, and so 

 gets diffused. In radiating, the rays pass from this 

 joint through the coffin bone, which is itself a radiating 

 structure, on to the ejittre base of the foot, the most 

 direct, therefore the shortest rays, as I have already 

 told you, pass out at the point of the frog. 



Let us stop a moment to consider the difference in 

 iiite7isity between focused and diffused rays. In the case 

 of light, you can focus with a magnifying glass the rays 

 on the back of your hand until you get an intensely 

 bright spot about the size of a pea, when all the rest of 

 the back of your hand appears in shade ; but move the 

 glass nearer to or further away from your hand, and you 

 see the bright spot becomes larger and larger, darker and 

 darker, until it ceases to be discerned as a spot at all, 

 and the back of your hand is not now in the shade, but 

 is faintly lighted up. The rays have radiated, and now 

 cover a wider area, dead faintly light up this area, instead 

 of lighting an area the size of a pea intensely and leaving 

 all the rest dark. This you can see. In your penny- 

 peep-show days you will no doubt have seen a large 

 muscular mountebank lie upon his back, and have a 

 large size forge anvil placed upon his chest, and this 

 struck by the swinging blow of a very large sledge- 

 hammer. The centre, or focus of weight, here is the 

 face of the hammer upon the anvil, and the rays have the 



