Contents xi 



water that has been boiled freezes more quickly when 

 exposed to cold, p. 49. How frost fertilises the earth, p. 50. 

 Why water dilates when frozen, p. 50. Why water is so 

 suitable for extinguishing fire, p. 51. Why spirituous liquors 

 never freeze, p. 51. Of the cause of elasticity, p. 52. On 

 the various ways in which rigid bodies can be bent, p. 52. 

 Perfectly rigid bodies cannot have their superficies either 

 lengthened or shortened, p. 54. Whence that arises, p. 55. 

 The convex side of a rigid body is carried towards the con- 

 cave side in the process of bending, p. 55. The matter of 

 the bent rigid body suffers compression, p. 56. Why, when 

 a rigid body is too much bent, it breaks in the middle, p. 56. 

 Why very solid bodies cannot be bent, p. 56. On the 

 manner in which bodies not so perfectly rigid bend, p. 57. 

 A certain rule which always holds good in natural effort to 

 accomplish anything, p. 57. Why it is that the thinner rigid 

 bodies are, so much the more easily can they be bent, p. 58. 

 The author's views as to the motion of restitution, p. 60. 

 Motion is set up by impulse alone, p. 61. Inanimate things 

 never begin to move spontaneously, p. 61. A certain subtle 

 mobile matter is always to be supposed, p. 61. The elastic 

 force of rigid bodies seems to arise from the impulse of 

 subtle matter, p, 61. Why a cord violently stretched con- 

 tracts spontaneously, p. 63. On the wonderful fracture of 

 glass drops, p. 63. Why fused glass becomes more con- 

 tracted in the process of cooling, p. 64. 



CHAPTER VII.— That the Elastic Power of Air is 

 DUE TO Nitro-Aerial Spirit. Also, of the 

 Manner in which Air is Impregnated anew with 

 Nitro-AErial Particles. Incidentally, of the 

 Elements of Fire and of Cold. 



Air is eminently elastic, p. 67. Why the skin rises into a 

 cupping-glass applied to it with a flame, p. 67. The elastic 

 force of air is diminished by burning, p. 68. That is proved 

 by experiments, pp. 68-71. wSomething aerial is required for 

 producing flame, p. 71. The air given out from the lungs of 

 animals has been in part deprived of elastic particles, p. 71. 



