6i 4 THE POPULAR SCIENCE MONTHLY. 



scenes of the distant past, to which the science of geology introduces 

 us, that I value it as a study, and wish earnestly to awaken you to its 

 beauty and importance. It is because it is the science from which you 

 will learn most easily a sound scientific habit of thought. I say most 

 easily ; and for these reasons. The most important facts of geology do 

 not require, to discover them, any knowledge of mathematics or of 

 chemical analysis ; they may be studied in every bank, every grot, 

 every quarry, every railway-cutting, by any one who has eyes and 

 common-sense, and who chooses to copy the late illustrious Hugh Mil- 

 ler, who made himself a great geologist out of a poor stone-mason. 

 Next, its most important theories are not, or need not be, wrapped up 

 in obscure Latin and Greek terms. They may be expressed in the 

 simplest English, because they are discovered by simple common-sense. 

 And thus geology is (or ought to be), in popular parlance, the people's 

 science the science by studying which, the man ignorant of Latin, 

 Greek, mathematics, scientific chemistry, can yet become as far as his 

 brain enables him a truly scientific man. 



But how shall we learn science by mere common-sense ? 



First, always try to explain the unknown by the known. If you 

 meet something which you have not seen before, then think of the 

 thing most like it which you have seen before; and try if that which 

 you know explains the one will not explain the other also. Sometimes 

 it will ; sometimes it will not. But, if it will, no one has a right to ask 

 you to try any other explanation. 



Suppose, for instance, that you found a dead bird on the top of a 

 cathedral-tower, and were asked how you thought it had got there. 

 You would say, " Of course, it died up here." But if a friend said : 

 " Not so ; it dropped from a balloon, or from the clouds ; " and told 

 you the prettiest tale of how the bird came to so strange an end, you 

 would answer : " No, no ; I must reason from what I know. I know 

 that birds haunt the cathedral-tower ; I know that birds die ; and 

 therefore, let your story be as pretty as it may, my common-sense bids 

 me take the simplest explanation, and say it died here." In saying 

 that, you would be talking scientifically. You would have made a 

 fair and sufficient induction (as it is called) from the facts about birds' 

 habits and birds' deaths which you knew. 



But suppose that when you took the bird up you found that it was 

 neither a jackdaw, nor a sparrow, nor a swallow, as you expected, but a 

 humming-bird. Then you would be adrift again. The fact of it being 

 a humming bird would be a new fact which you had not taken into 

 account, and for which your old explanation was not sufficient : and 

 you would have to try a new induction to use your common-sense 

 afresh saying, " I have not to explain merely how a dead bird got 

 here, but how a dead humming-bird." 



And now, if your imaginative friend chimed in triumphantly with, 

 " Do you not see that I was right after all ? Do you not see that it 



