G. P. Merrill — Composition of Stony Meteorites. 473 



It may be well to. acid that the approximate weight, so far as 

 known, of all the stones represented by these ninety-nine 

 analyses, w T as 4,014 kilograms or about 4'4 metric tons. An 

 average of 77 determinations, as given, of specific gravities 

 gave 3*51, of which the lowest, that of the Orgneil, France, 

 carbonaceous stone was 2*50. and the highest, that of Limerick, 

 Ireland, 3-92. 



It will at once be noted that there is a wide and striking 

 difference in composition between the meteorites and the ter- 

 restrial rocks, — a difference not merely in the relative propor- 

 tion of the various elements, but also, in one case at least, in 

 their method of combination. The most striking feature is, 

 for the meteorites (columns I and II), the low silica content, 

 and the high percentage of metallic iron, ferrous oxide, and 

 magnesia, with the corresponding low percentages of alumina, 

 lime, and the alkalies.* Compared with Washington's averages 

 for terrestrial rocks, it will be noted that there is a difference 

 of nearly twenty per cent in the amount of silica in favor of 

 the latter, and of some thirteen per cent in the amount of 

 alumina. These differences are so striking that they cannot 

 be considered as due to errors of analyses, or of their inter- 

 pretation. They must be fundamental. 



Should we disregard entirely the metallic iron of the meteor- 

 ites with its included nickel, cobalt, and phosphorus, and also 

 the iron disulphicle (amounting all together to 14*79 per cent), 

 and recalculate Analyses II on the basis of 100, we get the 

 results shown in column V below. In column YI is given 

 the average of seven analyses of terrestrial peridotitesf which, 

 as will be at once apparent to the petrographer, afford the 

 closest approximation, in chemical as well as mineral composi- 

 tion, to meteorites. These, it should be stated, have been 

 recalculated on a water-free basis. It is scarcely necessary, 

 however, to call attention to the fact that the peridotites repre- 

 sent the most basic of known terrestrial rocks, while the mete- 

 oric analyses which I have given represent the most acid type 

 that have come to us from space. It is evident, therefore, that 



* The composition as shown by these analyses does not, so far as sodium 

 is concerned, seem to harmonize with spectroscopic analyses, or Arrhenius' 

 statement »to the effect that the nucleus of comets, like the meteorites fall- 

 ing upon our earth, consists essentially of silicates, and partictdarly of the 

 silicates of sodium. See Worlds in Their Making, pp. 104-105. For the 

 benefit of those not familiar with the subject, it maybe well to state that the 

 principal mineral constituents of meteorites, aside from the metallic por- 

 tions, are the silicates of magnesia and iron, olivine and enstatite, with less 

 commonly monoclinic pyroxenes and basic feldspars. Silicates of sodium 

 must be rare, as shown by a simple glance at the analyses given. 



f The number was limited, since nearly all reported analyses were of 

 altered and highly hydrated examples, while for purposes of comparison 

 materials as nearly anhydrous as possible were needed. 



