Contents 



Untiring eye of the camera. Asteroids disclose them- 

 selves. Forty minutes with the camera does as much 

 as four years with the pencil. Unsought stars declare 

 themselves. What colours tell. Lines out . of place 

 in a spectrum mean much. The photography of 

 solar and stellar spectra. Twin stars separated. 

 The rings of Saturn proved to be meteoric. Helium 

 is first discovered in the sun, then on the earth. Evo- 

 lution demonstrated in the heavens as on earth. . . T, 



LYELL, SIR CHARLES 



UNIFORMITY IN GEOLOGICAL CHANGE 



The forces of nature at work to-day account for all 

 the past changes of the earth, because the processes 

 have occupied vast stretches of time. The testimony 

 of denudation and sedimentary deposition, of the 

 living creation, of subterranean movements. Abrupt 

 culminations of change are not inconsistent with 

 strict continuity of law. . . 105 



SHALER, NATHANIEL S. 

 RIVERS AND VALLEYS 



If we observe a shower on a hillside we see rivulets 

 which become miniature torrents as they unite. Swift 

 streams can move heavy stones. As a torrent slackens 

 in pace it deposits its stony freight. A stream becomes 

 a river when its banks become distinct and enduring. 

 Banks of rivers grow as sediment is deposited and 

 plants take root. The reasons why a river may run 

 zig-zag: the Mississippi as an example 139 



HUXLEY, THOMAS H. 

 THE SEA AND ITS WORK 



As waves fling gravel and stones at cliffs they carve 

 and mould them. Fantastic chisellings appear as 

 XX 



