xiv Contents 



CHAPTER XL— Of the A£rial Vortex, or Ascent 

 OF Sea- Water. Anglice : A Spout. 



Description of the said phenomenon, p. 125. It is caused 

 by a whirling motion of the air, p. 127. 



CHAPTER xn.— Of Light and Colours. 



Light does not consist of emanations from the luminous 

 body, p. 134. But of a certain impulse, p. 136. The 

 medium, by the impulse of which the rays of light are pro- 

 pagated, seems to consist of nitro-aerial particles, p. 136. 

 Whence comes the Hght of the glow- worm,- p. 137. Colours 

 and the images of things do not seem to be produced by 

 reflected light, p. 139. But by the impulse of a pecuHar 

 medium, p. 141. On the colour of glittering white, p. 144. 

 On white colour, p. 145. Why things which are black are 

 more easily burned by solar rays collected by means of a 

 mirror, p. 146. 



CHAPTER XIIL— Of Lightning. 



Lightning does not seem to arise from kindled exhalations, 

 p. 147. How thunder is produced, p. 148. Lightning seems 

 to consist of nitro-aerial particles thrown into motion, p. 149. 

 In what way very sultry weather can be produced by unequal 

 motion of the air, p. 149. Whence the force of lightning 

 arises, p. 150. Why a thunderbolt sometimes fuses a sword, 

 leaving the sheath intact, p. 151. On the cause of death of 

 animals struck by lightning, p. 152. On violent winds 

 accompanying thunderstorms, p. 152. 



CHAPTER XIV. — Of the Heat of Quicklime. 

 Incidentally, of the Combination of Opposite 

 Salts. 



The heat of quicklime moistened with water does not 

 seem to arise from igneous particles simply fixed in it, p. 

 154. But from the heat produced by contrary salts, p. 154. 



