INTRODUCTION. 



nising the operation of Law and of Design. In the 

 material framework of this world, substances and forces 

 present themselves in definite and stable combinations. 

 All things are not in perpetual flux, as ancient philoso- 

 phers held. Element remains element ; iron changes not 

 into gold, nor oxygen into hydrogen. With suitable pre- 

 cautions we can calculate upon finding the same thing 

 again endowed with the same properties. The con- 

 stituents of the globe, indeed, appear in almost endless 

 combinations ; but each combination bears its fixed cha- 

 racter, and when resolved is found to be the compound of 

 definite substances. Misapprehensions must continually 

 occur, owing to the limited extent of our experience. 

 We can never have examined and registered possible ex- 

 istences so thoroughly as to be sure that no new ones will 

 occur and frustrate our calculations. The same outward 

 appearances may cover any amount of hidden differences 

 which we have not yet suspected. To the variety of 

 substances and powers diffused through nature at its 

 creation, we must not suppose that our brief experience 

 can assign a limit ; and the necessary imperfection of our 

 knowledge should be ever borne in mind. 



Yet there is much to give us confidence in science. 

 The wider our experience, the more minute our examina- 

 tion of the globe, the greater the accumulation of well- 

 reasoned knowledge, the fewer must become the failures 

 of inference compared with the successes. Exceptions to 

 the prevalence of Law are gradually reduced to Law 

 themselves. Certain deep similarities have been detected 

 among the objects around us, and have never yet been 

 found wanting. As the means of examining distant parts 

 of the universe have been acquired, those similarities have 

 been traced there as here. Other worlds and stellar 

 systems may be almost incomprehensively different from 

 ours in magnitude, condition and disposition of parts, and 



B 2 



