56 SPECIALIZATION IN NATURAL SCIENCE. 



intended to be a pictorial instruction book for element- 

 ary schools, and the second as a cyclopedic manual of 

 science — a text-book for the universities of the da) r . 

 For these purposes they were the standard treatises of 

 those times. 



Now set over against these the academic and college 

 text-books of to-day, and mark the difference. On any 

 single topic alone of scientific instruction out of more 

 than a dozen at least, our text-books comprise more in- 

 formation in a very concentrated form than does either 

 of these volumes. But it is by trying to estimate the 

 number and cost of technical works in the various 

 special departments that we begin to realize the extent 

 of our modern special fields of science ; for their litera- 

 ture is enormous in quantity and in expense. 



How feeble is the popular apprehension of the latter 

 fact! 



This is partially illustrated by the often asked ques- 

 tion, " What is a good standard work which I can get 

 to tell me the names of the insects that I collect V ' 

 Such an inquirer has not had even a glimpse into the 

 vastness of the special field of the modern entomologist. 

 For it is now estimated that there are no less than ninety- 

 thousand species of beetles to be described, and twenty- 

 four thousand of two-winged flies, and twenty-five thou- 

 sand of four- winged flies like the bees, and twenty -five 

 thousand of butterflies and moths, which, with eight 

 hundred species of centipedes and four thousand of 

 spiders, make no less than one hundred ninety thousand 

 species of insects. Even our own North American share 

 of these would fill volumes on volumes of descriptive 

 matter. 



It is sufficiently evident that the facts and principles 

 of any one general department of modern science, have 

 been developed to proportions too vast to be easily 

 grasped by one mind, as in former years. The greater 



