CHAPTER XIII.

The ether. Its nature considered. Behaves like a gas 226 Can be pumped out of a receive 227 Light and heat do not pass through a tube _in vacuo_. Laboratory experiments examined 228 Light and darkness in a partial vacuum, though high 229 Electricity not a carrying agent 230 Why there are light and dark strata in a high vacuum 232 The real carrying agent through a high vacuum is the residue of ether left in it. Digression to consider the aurora 233 How air may be carried to extraordinary heights. Zones of air carried up are made luminous by electricity 234 Comparison of this method with experiments quoted 236 Experiment suggested to prove whether light passes freely through a vacuum tube 237 The ether does not pervade all bodies freely 238 It must be renounced altogether or acknowledged to be a material body, subject to expansion, condensation, heating or cooling 239 How light and heat pass through glass 239 Temperature of the ether variable. Zodiacal light, cause of 240