1 66 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



as a rule the fragments which fall are small, sometimes merely 

 a dust-shower. The fact that many meteorites consist wholly 

 of metallic iron (with nickel), while others contain a large 

 intermixture of iron grains in a matrix of silicates, indicates 

 that iron plays a greater part in the composition of the 

 planetoids than in that of terrestrial rock-material, in which it 

 almost always occurs in combination with oxygen or sulphur. 



In the year 1870 Nordenskiold discovered on the coast of 

 the Greenland island Disko, near Ovisak, gigantic blocks of 

 solid nickelic iron weighing several thousand kilogrammes. 

 These were at first thought to be meteoritic, until Steenstrup 

 and Daubree showed that the basaltic rocks of Disko contain 

 greater and smaller inclusions of iron, which are identical with 

 the great blocks in every particular. It would thus seem that 

 considerable masses of iron are actually present in the interior 

 of the earth, as has been assumed from the earth's specific 

 gravity. 



Sir Norman Lockyer in a recent work, The Meteoritic 

 Hypothesis (1890), has attributed a very important part to 

 meteorites in cosmology. He regards all luminous cosmic 

 bodies as masses which have originated from swarms of 

 meteorites, or from the collision of vapours to form a cosmic 

 sphere. 



Geogeny. During the nineteenth century speculations regard- 

 ing the earth's origin followed for the most part the nebular 

 theory of Kant, Herschel, and Laplace, and assumed that the 

 earth, in common with all other cosmical bodies, originated by 

 the condensation of some part of universal matter. It was 

 raised to a glowing heat during the process of condensation, 

 and after a protracted period of cooling a solid crust began to 

 form on the exposed surfaces. 



This theory was further established by Fourier in 1820, and 

 by Poisson in 1835. Nevertheless, the Neptunian doctrine 

 which had flourished in the end of the eighteenth century, 

 under the influence of Werner, was again resuscitated, and its 

 adherents passed under the name of .Neo-Neptunists. The 

 Munich chemist Fuchs was the leader of the Neo-Neptunists, 

 and amongst his followers were Schubert, Schafhautl, and 

 Andreas Wagner. Their conception of the beginning of the 

 earth was literally the same as that given by the Bible, 

 " In the beginning the world was empty and void." 



