364 DIVERSIONS OF A NATURALIST 



an atmosphere of self-deception and of readiness to be 

 deceived by others to which misplaced confidence in 

 their own cleverness and power of detecting trickery 

 renders many — one may almost say most — people 

 victims. The physician who has given his life to the 

 study of mental aberration and diseases of the mind is 

 the only really qualified investigator of these " marvels," 

 and no one who has closely studied what is known in 

 the domain of mental physiology and pathology has 

 any difficulty in understanding, and bringing into 

 relation with large classes of established facts as to 

 illusions and mental aberration, the " beliefs " in magic 

 and second-sight which are here and there found flourish- 

 ing at the present day, as well as the, at first sight 

 startling, evidence of highly accomplished men who have 

 Suffered from such delusions. 



Leaving aside all these more extreme cases of what 

 we may call " challenges " to science, let me cite one 

 or two of the more ordinary classes of cases in which 

 science is either attacked or treated with disdain by 

 modern wonder-mongers. It was declared by a writer 

 in the eighteenth century that, after all, human know- 

 ledge is a very small thing, since we cannot even tell 

 on one day what the weather is going to be on the 

 next ; still less can we control it. That remains 

 perfectly true to-day, although by the hourly observation 

 and record of the movements of " areas of depression " 

 in the atmosphere and the telegraphic communication 

 of these records from all parts of the Atlantic region 

 of the northern hemisphere to central stations, a very 

 important degree of accuracy in foretelling gales, and 

 even minor changes of weather, has been reached. Side 

 by side with this organized study of the movements of 

 " weather " we still have the so-called " almanacs," in 



