COMMON THINGS THE EARTH. 



a degree, we should have to multiply it by three hundred and 

 sixty, by which we should obtain the circumference of the earth. 

 This would give twenty-five thousand and twenty miles, and we 

 should then find by the usual mode of calculation the diameter of 

 the earth, which would prove to be a little under eight thousand 

 miles. 



The fact that a degree of the earth's circumference consists in 

 round numbers of just so many thousand feet as there are days in 

 the year, supplies a very convenient aid to the memory. 



We have made these calculations chiefly with a view of render- 

 ing the principles of the investigation intelligible. The more 

 exact dimensions of the earth will be explained hereafter. 



"We conclude, then, that the earth is a globe eight thousand 

 miles in diameter. 



9. To enounce this stupendous arithmetical result is much 

 easier than to obtain any distinct notion of the actual magnitude 

 which it expresses. Such a globe has a circumference of twenty- 

 five thousand miles. A locomotive engine travelling incessantly 

 night and day, at twenty-five miles an hour, would take about 

 forty-two days to go round it. 



10. When the diameter of a globe is known, its surface and 

 volume or cubical bulk can be easily determined. To find the surface 

 we have only to take three hundred and fourteen hunditedths of 

 the square of the diameter, and to find the volume, five hundred 

 and twenty-four thousandths of the cube of the diameter. In this 

 way we find that the surface of the earth measures two hundred 

 millions of square miles, and that its cubical bulk is about two 

 hundred and sixty thousand millions of cubic miles. 



If the materials which form such a globe were built up in the 

 form of a vertical column, the base of which would have the mag- 

 nitude of England and Wales, its height would be nearly four 

 and a half millions of miles ! 



11. Such being the dimensions of the globe we inhabit, we are 

 next to consider what is its condition as to motion. Is it, as it 

 appears, at rest ? For several thousand years in the history of 

 the human race, it was not only so considered, but he that would 

 have ventured to call in question its stability and quiescence 

 would have been deemed insane. Certain expressions in the sacred 

 Scriptures being erroneously supposed to affirm its immobility, it 

 was deemed heretical to deny it ; and Galileo, who did so, was 

 put to the torture by the ecclesiastical authorities of the day, and 

 compelled to admit its quiescence. This verbal admission was, 

 however, so utterly opposed to his convictions, that, on quitting 

 the presence of the inquisitors, he stamped on the ground, and 

 muttered the words, " It moves for all that." 



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