A Penny Weekly Magazine of Natural History. 



No. U9. SEPTEMBER 16th, 1882. Vol. 3. 



MISTAKES. 



NOTHING is so easy as to make 

 a mistake. It is recorded of 

 Kepler, in his investigations into tlie 

 laws regulating the distances of the 

 planets and their periods of revolution, 

 that an error in his calculations de- 

 layed the final discovery for many a 

 weary month. Newton, too, could not 

 satisfy himself that his law of gravita- 

 tion w^as correct until a more accurate 

 measurement of the diameter of the 

 earth was substituted for that he had 

 used. So in natural history many an 

 error has been unintentionally commit- 

 ted that has delayed and hindered pro- 

 gress. But while mistakes of this class 

 are really few and far bct«-een, however 

 important may be their cffccls, tlicre 

 is another class of errors that can be 

 guarded against in most cases — the 

 mistake of coming to a conclusion 

 without sufTicicnt knowledge. Some 

 people imagine that they know evcry- 

 iliing, or so nearly cvcrvlhiiig as (o 

 amount to the same thing. These 

 people are generally densely ignorant 

 and scarcely know anything at all, but 

 what they lack in knowledge is abun- 



dantly made up in conceit. They will 

 name a bird on the wing with unerring 

 certainty ; tell you what a plant is so 

 soon as the cotyledons are above the 

 ground ; there is no moth they do not 

 know, and but few larvae; and, in 

 short, the difficulty is to puzzle them. 

 But the perfect confidence these sort 

 of people have in themselves is very 

 likely to mislead a beginner. A cap- 

 tured pug is taken to them, — a cursory 

 glance is taken at it, — " Oh ! yes ! it 

 is lariciala." The same specimen is 

 taken to a much better entomoloj^ist : 

 it is carefully examined, compared with 

 two or three different species, questions 

 asked as to where and when it was 

 taken, and then he declines to s.iy what 

 it is until he has an opportunity of 

 examining it in daylight. Now if the 

 owner of the pug, as is most probable, 

 knows nothing of the difficulty of 

 naming a worn Eup'U/iccia, he would 

 naturally conclude that the person who 

 professetl to recognize it at first sight 

 knows most about them, and that what 

 was easy to him was a puzzle to the 

 other. Yet it was probably not lari- 

 data at all, perhaps not even like it. 



