394 STUDIES FOR STUDENTS 



the Older of their relative abundance, with the eight most 

 important elements of the earth's crust placed in similar order. 

 The list of the latter is taken from Roscoe and Schorlemmer.' 



METEORIC SERIES TERRESTRIAL SERIES 



1. Iron I. Oxygen 



2. Oxygen 2. Silicon 



3. Silicon 3. Aluminum 



4. Magnesium 4. Iron 



5. Nickel 5. Calcium 



6. Sulphur 6. Magnesium 



7. Calcium 7. Sodium 



8. Aluminum 8. Potassium 



It should be remembered in drawing conclusions from the 

 above list that the elements of cosmic matter in its entirety are 

 here compared with the elements of only the crust of the earth ; 

 further, that the meteoritic matter now known probably does not 

 show a true proportion of stony matter. As I have shown else- 

 where,'' the iron meteorites are much more likely to be known 

 and preserved than the stony. It is probable, therefore, that if 

 the average composition of meteoritic matter were known, iron 

 would not occupy so high a place as it does in the above table. 

 The relative excess of magnesium and nickel, and scarcity of 

 aluminum and calcium in meteoritic, as compared with terrestrial, 

 matter may be due to the same cause. 



COMPOUNDS 



The elements of meteorites chiefly occur combined. The 

 exceptions are iron, nickel, cobalt, and copper, all of which 

 occur largely in the form of alloys, carbon, and the gases, 

 hydrogen, and nitrogen, probably held as elements in the pores 

 of meteorites. 



The compounds of meteorites according to the mineralogical 

 names by which they are generally known, and roughly in the 

 order of their relative abundance, are as follows, the minerals 

 not occurring upon the earth being printed in italics : 



'Treatise on Chemistry, Vol. I. 'Jour. Geol., Vol. V, p. 126. 



