2 4 o POPULAR SCIENCE MONTHLY. 



from what they are to-day. This is astronomical work of importance 

 awaiting research. 



We desire to know much more concerning the individual planets. 

 Even-body asks, 'Are the planets inhabited?' and no favorable answer 

 has yet been given. If one means by the question, inhabited by such 

 beings as we are structurally, then one can say that if one of us were 

 transported to any of the planets we could not live there a minute. 

 Some, like Jupiter, are too hot; others, like the moon, too cold, or 

 without air to breathe or water to drink, or with too great or too little 

 gravity for our bodies. One does not need to assume such likeness, 

 especially since we know something of the past history of man and 

 animals on the earth, adapted to it in form, size, structure, habits 

 and intelligence all correlated. To assume intelligence of our type 

 is hardly allowable any more than for structures like ours. Vertebrate 

 skeletons are not necessarilv the onlv form in which intelligence of 

 high type may abide. The implements and skill of the astronomers 

 are yet to determine what can be learned about this question. Taking 

 what we know about the development of life on earth, it would seem to 

 be insanely improbable that among the millions of millions of huge 

 bodies in the universe, all apparently made of the same kinds of matter 

 and subject to the same laws, that the earth is the only one among 

 them all to have life and mind developed upon it. But at present 

 we do not know that it may not be true. Let the twentieth century 

 find out. 



Geology: The whole of geology was a gift of the nineteenth 

 century. There was nothing that deserved the name before it, yet 

 more than half of the land of the globe has not yet been surveyed, 

 and many geologic problems are yet unsettled, concerning regions that 

 have been studied. The mineralogical relations and precedents among 

 basalts, granites and other rocks, as well as the physical conditions 

 that determined composition, arrangement and distribution, remain 

 to be determined. Volcanic phenomena are not at all well under- 

 stood. The composition of the interior of the earth is quite unknown; 

 its temperature, and the rate of heat conductivity of the various rocks 

 — questions which, when answered, will have much to say about the 

 age of the earth and especially of the length of time since it has been 

 a habitable body for any living things. At present there are two 

 camps interested in this question, with lower time limits from ten 

 million to a thousand million years. When Asia, Africa and South 

 America have been as well studied as Europe and North America have 

 been, there will probably be found vast stores of metals, coal, oil and 

 valuable minerals, thus adding to the world's stock of needful things. 

 Also the discovery of new varieties of fossils, the ancestors of living 

 species, especially of mankind, missing links, will add to the interest 

 in human affairs. Geologists have for years been trying to find some 



