4 o6 THE POPULAR SCIENCE MONTHLY. 



sented by millions of years will be, not the disappearance of the 

 dry land, bnt that of the sea, which, accompanied by all the 

 fluids, will gradually infiltrate through the crust with which our 

 planet is covered. 



The certain feature in M. de L'Apparent's essay is that, before 

 the eternal drought comes on, the terrestrial relief will be leveled. 

 The continental surface will have become an immense plain, in 

 which the Alps, Himalayas, and Andes will be only little hills. 

 The fertility of the soil will be augmented by the considerable 

 formation of vegetable earth, which will at the same time be de- 

 prived of sufficient watering by the rarity of rain. Climates, lit- 

 tle as we may suppose them to be modified by the decrease of the 

 luminous and calorific energy of the sun, will be entirely trans- 

 formed. It seems to M. Leotard, in short, that the phenomena 

 contributing to the destruction of the continents will diminish 

 continuously in intensity, while the natural influences tending to 

 result in the desiccation of the surface of the globe will gather 

 energy in the course of ages, preparing for our planet the curious 

 future just described a future which will, however, be post- 

 poned so far that mankind will not be a witness of that end of 

 terrestrial evolution. 



Another writer in the Revue Scientifique (H. S.) has called at- 

 tention to what the land is gaining, believing, in view of the uni- 

 versal stability of affairs, that it must be equal to the losses. The 

 land gains everything, including cosmic dust and meteorites, that 

 falls from space; it gains all the gases that are continually under- 

 going solidification in flesh and wood, with which they become 

 incorporated ; and it gains the shells of all the molluscs, infusoria, 

 etc. With a very insignificant part of what these infinitely small 

 beings have left it has been possible to build cities larger than 

 Paris ; and the Great Pyramid may be said to be the work, not of 

 King Cheops, but of the nummulites. If a well-informed person 

 should follow out all the facts bearing on the subject, he would 

 probably find a complete equilibrium, an admirable compensa- 

 tion existing between the gains and the losses of the crust of the 

 earth. 



M. de L'Apparent has replied to M. Leotard's criticism that it 

 rests on a misunderstanding which can be easily dissipated. In 

 the summer of 1890, he says, " I discussed, in the Geological Soci- 

 ety of France, the general question of erosion, not to predict the 

 actual leveling down of the dry land, but simply to arrive at a 

 method of estimating the duration of the geological periods. My 

 reasoning was as follows : If the present causes of destruction (me- 

 chanical and chemical action of running waters and marine ero- 

 sion) continue to act in the same measure as now, without any- 

 thing intervening to disturb their working, the continental relief 



