CONTENTS. XVil. 



CHAPTER XXIIL 



TOLCANOBS AND EARTHQUAKES. 



Another popular fallacy. The earth's internal fire. Dr. Mayer's theory. 

 Dr. Tyndall opposed to it. Dr. Mayer's dogged assertion. Selfish- 

 ness of men ot science. Herschell on Volcanoes. The earth and 

 an egg. Objection to Herchcll's theory. Explanation of Volca- 

 noes. Why Volcanoes become extinct. Coal gas. -Mount St% 

 Helena and Sulphur Springs.- Prof. Mallet on Water and Volca- 

 noes. Cause of Earthquakes. Prevention of Earthquakes. Oil 

 boring in Pennsylvania. llerschell's extraordinary theory of Earth- 

 quakes. What ho knew of chemical action in the interior. The 

 necessity for scientific men not taking anything tor granted^ 1 53 160. 



CHAPTER XXIV. 



THE TIDES. 



The regnlarity of the Tides. The influence of the new and full moon on 

 the Tides. There must be one grand cause of the Tides. This is 

 pressure, not attraction. Cause of variation in the Tides by the 

 position of the moon. Formation of the Land. Winds. Lardner's 

 theory of the Tides. Its fallacy shewn. The earth ought to be 

 approaching the moon. Facts to be remembered. The Plane of the 

 Ecliptic. The effect of pressure on the atmosphere. The Tides 

 caused by pressure in passing the Plane of the Ecliptic. The 

 moon's atmosphere. The Tide in the Mediterranean. The Bay of 

 Fundy Tides seventy feet high. Ram Pasture. Rise of two feet in 

 three "miles. -Tbe repelling forces control the Tides, . . . 161 166. 



CHAPTER XXV. 



GULP STREAM AND DEEP SEA CURRENTS. 



The cause of the Gulf Stream. Dr. Carpenter's theory. Oceanic 

 Circulation.- Experiment with glass trough. No comparison. 

 Strength of Polar Currents. Channel between Faroe Islands and 

 Shetland. Dr. Wyville Thompson differs from Dr. Carpenter. 

 Reciprocal circulation of Water and Air. Beautiful theory of 

 Atmospheric Circulation overbooked by Dr. Carpenter. What 

 causes the cold deep waters . . > > . . 167 172 



CHAPTER XXVL 



COMETS. 



Very little known about Comets. Facts about them. Jupiter's Influent* 

 on them. -Comet of 1680. Herschell's description of it. Tht 

 movements of a Comet different from a Planet All the heavenly 

 bodies, Magnets. The motions of Comets explained on this theory. 

 How Comets are made periodic. Encke's and Biela's ComeU. 

 "The atmospheres of Comets. Their tails. Their purpose. Art 

 they inhabited ?.*. *...,.., ....^..... ..173177 



