KEY AND INDEX 



knowledge in all its departments, and the application 

 of that knowledge to the affairs of every-day life. 



So general a characterization, of course, can convey 

 but a vague impression to the mind. To make this 

 impression somewhat specific, let us say that there 

 are six or seven large groups of subjects that form the 

 theme of our successive chapters. These might be 

 summarized in various ways, but perhaps the follow- 

 ing somewhat arbitrary classification will serve as well 

 as another: 



1. Cosmical Sciences, as specifically represented by 

 the science of astronomy, with its practical applications 

 to the art of navigation. Here we have to do with the 

 ferreting-out of the secrets of the starry universe and 

 the planetary systems, from the visionary interpreta- 

 tions of the ancient Egyptian and Babylonian star- 

 gazers to the accurately measured records of the 

 modern observer, equipped with telescope, spectro- 

 scope, and photographic plate, or with sextant and 

 compass. 



2. Telluric Sciences; specifically, geography, geology, 

 paleontology, and meteorology. Here we deal with 

 those studies through which a knowledge of the earth's 

 geographic masses and of its rocky structure has been 

 gained; with interpretations of the method of world- 

 building that have been made possible by the study 

 of fossil remains; and with the investigations of at- 

 mospheric phenomena to which the modern practical 

 science of weather prediction owes its origin and its 

 success. 



3. Physical Sciences, or what the students of the 

 elder day termed natural philosophy, including the 

 phenomena of gravitation, heat, light, sound, and 

 electricity and magnetism. This is a field at once of 

 the most obvious interest and the utmost practical 

 importance. Not only do its studies have to do with 



