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POPULAR SCIENCE REVIEW. 
casting weather, Sunspots must remain of very secondary im- 
portance. It must be remembered, tbat science, like politics, 
bas a practical and a purely theoretical side ; and tbat while 
Fig. 3. Curves showing Summer and Winter temperatures in the years 
1867-1877 inclusive. 
evidence of the correctness of a theory, even if it be of the very 
slightest character, is a reward amply sufficient to the theoreti- 
cal student, proof that the theory is of practical importance is 
