THE BOWELS OF THE EARTH. 307 



covery of some sizable lumps of black diamond in the Canon 

 Diablo meteorite led Mr. Huntington to investigate further in the 

 very extensive collection belonging to Harvard University, and 

 he found, on dissolving sample chips as thoroughly as possible, 

 that a powder remained whose resistance to corrosives and in- 

 vincible hardness are signs manual of the sovereign of stones. 

 We find, too, in these iron meteorites gases absorbed, such as 

 those at whose door we have laid the responsibility for the pro- 

 duction of volcanic eruptions. 



Since the weight of our earth and the evidence of sample 

 fragments of planetary matter point to its being mainly iron if 

 we may not only say that this is an iron age but also an iron 

 world is it any wonder that iron is so widely distributed, or that 

 it is the universal pigment, even dyeing the blood of our veins ? 

 But there is further evidence on these lines at which we have as 

 yet but hinted. We said that meteorites were connected in com- 

 position with terrestrial rocks. It is in fact true that native iron 

 similar in structure to that of meteorites is found in some basaltic 

 dikes in Greenland as large masses, and in microscopic quantities 

 elsewhere, and it seems almost certain that it has been torn from 

 the depths of the earth. The rock in which the diamonds occur in 

 the Kimberly mine (and everywhere else where they occur origi- 

 nally, and not in sand and gravel, they are in similar connection) 

 is very rich in iron, is composed of minerals common in meteor- 

 ites, but is devoid of quartz and feldspar, the commonest minerals 

 of the upper crust. Practically, all the minerals of the meteorites 

 occur native in the earth's crust, but only sparingly, except in 

 connection with rocks that have risen through fissures from be- 

 neath. They do not occur in connection with all these rocks, 

 but only in connection with rocks like the Kimberly rock, which 

 are darker and heavier and less siliceous. There are a number 

 of reasons for supposing that these darker and heavier igneous 

 rocks, containing more iron and less silica, have a deeper source 

 than those composed mainly of quartz and feldspar, but we will 

 mention only one. Our earth is wrapped with an atmosphere of 

 oxygen, an element exceedingly ready to enter into combination 

 so much so that in all our ordinary surface rocks all the other 

 elements are combined with oxygen as much as can be. Now 

 iron, as is well known, has the power of combining with oxygen 

 either in the proportion of three of oxygen to two of iron or 

 in even proportions. The former compounds which have more 

 oxygen are those found in ordinary rust, and are much more 

 readily formed, being the so-called ferric compounds. They are 

 often yellow or red in color. The other compounds containing 

 less oxygen the so-called ferrous compounds very readily ab- 

 sorb more oxygen. In fact, their readiness to do so under the 



