THE EARTH AT ITS BEGINNING 



we can see in their extinct form on the Moon ; but 

 they were destroyed by these outflows of lava of which 

 we have spoken. 



Then, still cooling, the earth's crust grew thicker and 

 thicker. The great outflows and eruptions of molten 

 elements from underneath grew fewer, and more liquid 

 elements cooled into solids, and more gases condensed 

 into liquids. There was another thing happening of 

 which, as conscientious recorders of the history of the 

 earth^s geology, we must take note ; and it is that in 

 those early days meteorites were falling on the earth 

 in vastly greater numbers than they do to-day. Meteor- 

 ites are masses of cooled rock flying through space which 

 still occasionally fall on the earth, and specimens of them 

 are still to be found, many of them preserved in museums, 

 such as the Natural History Museum in Cromwell Road, 

 London. But the earth in its path has swept most of 

 them up, as the housemaid's dusting-pan collects the 

 fragments of dust. When the earth was young there 

 were incomparably more fragments to collect, and they 

 fell on the earth like rain. 



Meanwhile the cooling water vapour became the 

 oceans ; clouds and rain and cool winds and eventu- 

 ally snow and ice became possible; and the hardening 

 lavas, or fire- born rocks, became subject to their influences, 

 till above them were raised the stratified rocks, of which 

 we have spoken in our earlier chapters, and the lineage and 

 descent of which is part of the study of geology. On the 

 earth most of the traces of its earlier history have been 

 removed, but there are some signs of them perceptible to 



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