beyond this line, certainly is such as would arise, was all 

 the heat so measured, the result of the passage of the 

 heat by conduction through the crust of rocks. 



Whether or not the subterranean bands of equal heat 

 have any strict relation, upon a large scale, to the 

 isothermic lines which have been traced around most 

 portions of our globe, is a point which has not yet been 

 so satisfactorily determined as to admit of any general 

 deductions. 



The Oriental story-teller makes the inner world a 

 place of rare beauty a cavern temple, bestudded v. ith 

 self-luminous gems, in which reside the spiritual beings 

 to whom the direction of the inorganic world is confided. 



The Philosopher, in the height of his knowledge, has 

 had dreams as absurd as this ; and amid the romances of 

 science, there are not to be found any more strange visions 

 than those which relate to the centre of our globe. At 

 the same time it must be admitted, that many of the 

 peculiar phenomena which modern geological researches 

 have brought to light, are best explained on the hypo- 

 thesis of a cooling sphere, which necessarily involves the 

 existence of a very high temperature towards the 

 centre. 



We have already noticed some remarkable differences 

 between solar and terrestrial heat ; but a class of observa- 

 tions by Delaroche* still requires our attention. Solar 

 heat passes freely through colourless glass, whereas the 



* From his experiments, the following conclusions were arrived 

 at by M. Delaroche : 



1. Invisible radiant heat may, in some circumstances, pass 

 directly through glass. 



2. The quantity of radiant heat which passes directly through 

 glass is so much greater, relative to the whole heat emitted in 

 the same direction, as the temperature of the source of heat is 

 more elevated. 



3. The calorific rays which have already passed through a 

 screen of glass, experience, in passing through a second glass 

 screen of a similar nature, a much smaller diminution of their 

 intensity than they did in passing through the first screen. 



