large ones which are over one-half inch. In a microscope 

 section it is quite easy to see chondrules and occasionally a 

 meteorite is found where they are so abundant they crumble 

 away into one's hand. Chondrules are unique to stone me- 

 teorites. They are not found in any terrestrial rock. Fortu- 

 nately, the great majority of stone meteorites, 94% of them, 

 are chondrites. The other 6% are achondrites, which means 

 "without chondrules." It is difficult to distinguish achon- 

 drites from some kinds of terrestrial rocks, especially the 

 common rock basalt, and sf>ecial, often elaborate, testing is 

 required in some cases. 



Stone-iron meteorites consist either of irregular lumps 

 (not chondrules) of olivine contained in a network of metal 



to tell what chemical elements arc present in the star, and 

 from the relative intensities of the colors characterizing them 

 it is possible to determine the relative quantities of these 

 elements. 



Now, as it turns out, most stars consist dominantly of the 

 element hydrogen along with small quantities of other chem- 

 ical elements. Indeed, the entire universe consists mostly 

 of hydrogen (over 93%). When the spectroscope was first 

 turned on the nearest star to the earth, namely, the Sun, 

 hydrogen was found along with a small, but significant per- 

 centage of other elements: calcium, oxygen, silicon, magne- 

 sium, aluminum, iron, sulfur, phosphorus, sodium, potas- 

 sium, carbon, nickel, cobalt, etc. When the relative amounts 



Chondrules shown against a one-inch scale illus- 

 trate the range of sizes among individual chon- 

 drules. They are unique to stone meteorites. 



Cross-section of chondrule (light, round area) in the Ensis)ieim 

 chondrite meteor depicted in the wood cut. (Magnified IfO times.) 



(these are called the pallasites) or a filigree of metal con- 

 tained in a mass of mostly pyroxene (these are called the 

 mesosiderites) . In either case no stone-iron could be mistaken 

 for any terrestrial rock. They have a unique appearance. 

 Knowing the chemical composition of meteorites, espe- 

 cially the largest group of them, the stone meteorites, per- 

 mits us to make a series of deductions that would delight 

 Sherlock Holmes. In the last century a device called a spec- 

 troscope was invented. It permits one to take the light of a 

 star, concentrate it by a lens system, and break it up into its 

 spectrum of colors. In such hot objects as stars the chem- 

 ical elements that compose them are constantly emitting 

 light, and each element has a characteristic group of colors 

 it emits. When all the colors from all elements in a given 

 star are blended together, as they are when they are emitted 

 from the star, the star generally appears white. The spec- 

 troscofje is designed to imblend them back to the individual 

 colors of the elements that emitted them. Thus it is possible 



of these were compared with stone meteorites it turned out 

 that, element for element, they were almost identical, but 

 different from other observed stars. Furthermore, when 

 compared with the surface rocks of the earth's crust, the 

 compositions are quite different. From this we can deduce 

 that these elements, which form the solid minerals of meteo- 

 rites, in the same relative proportions, were derived from 

 matter being boiled off the Sun and condensing into solids. 

 [The large amount of hydrogen, which is a gaseous element, 

 does not condense into these solids and thus does not enter 

 into the formation of solid objects in the solar system. It 

 exists mostly as a thin, interplanetary gas, and partially as 

 gas trapped between the mineral grains of solid objects.] 

 The condensation process would involve cooling and the 

 combination of elements together into minerals and the so- 

 lidification of these molten droplets of minerals into solids. 

 These droplets would be the chondrules observed in the ma- 

 jority of meteorites. Thus meteorites are, with a high prob- 



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