30 PRESIDENTIAL ADDRESS SEe'lION ii. 



Certain meteorites contain hydrocarbons — compounds re- 

 sembling terrestrial bitumens or petroleum. These are volatile 

 and combustible substances, and their presence shows thai such 

 meteorites could not have been subjected to great heat subse- 

 quent to the formation of the hydrocar1)ons, and that the heating, 

 as the pass through the earth atmosphere, has been only 

 superficial. All meteorites contain included gases, such as 

 hydrogen, carbon monoxide, carbon dioxide, marsh-gas, and 

 sometimes nitrogen. Terrestrial igneous rocks can also be 

 made to give off similar gases. 



In contrast to the average rocks of the Earth's crust, 

 meteorites show an excess of iron, nickel, and magnesium, and 

 what is especially noteworthy an almost entire absence of water, 

 free oxygen, and free silica. The more important rock-forming 

 minerals of the earth's crust are absent, such as quartz, ortho- 

 clase, the acid plagioclases, micas, and amphiboles, the chief 

 minerals of the meteorites being present only in small proportion 

 in the crust. The crust rocks of the earth abound in free silica. 

 lime, alumina, and alkalies, while meteorites abound in iron, 

 nickel, and magnesia. The minerals of meteorites are always 

 unaltered, and show no signs of weathering; there are no 

 hydrated minerals, and there are no minerals present (such as 

 the zeolites, cpidote, tourmaline, etc.), in the formation of 

 which water or water-vapour takes part. 



These facts point to the conclusion that the jjarent body 

 from which meteorites were deriv^ed had no water nor an 

 oxygen-bearing atmos])here, having ])robably been too small to 

 retain their gases in a free state. In this case there could have 

 been no selective weathering of its materials, and no mineralogical 

 differentiation of the terrestrial type, and therefore no forma- 

 tion of the terrestrial type of crust. The atmosphere and 

 water of the earth have been largely instrumental in the forma- 

 tion of its particular kind of crust, and the free silica of the 

 earth's crust is easily accounted for l)y tlie working over and 

 over of its original constituent materials l)y their agencies. By 

 the exposure of the silicates to car])on dioxide the bases are 

 changed to car]:)onates, and silica is set free. 



Most of the above facts regarding meteorites and what they 

 imply have been pointed out Ijy Farrington and others in their 

 studies of the structure and composition of meteorites, and 

 Farrington also concludes from their structure, that the material 

 of the parent body was arranged according to density, and had 

 cooled from a liquid or semi-liquid state before disruption. 



Finally, Chamberlin further considers that the meteorites 

 of the erratic type are merely the incidental products of stellar 

 systems, and that the meteoritic condition does not seem to 

 represent a generative method whereby stellar systems are 

 evolved. 



It is not unreasonable to suppose from the characters of 

 meteorites, and in view of the known uniformity of matter in 



