DARKNESS OF UNDISCOVERED TRUTH. 215 



In consequence of the almost infinite complexity of 

 matter and its forces, there occur in every physical and 

 chemical action very many other effects besides those 

 which we are accustomed to anticipate or observe. The 

 various effects produced simultaneously in iron by raising 

 its temperature to full redness, have been already men- 

 tioned ; l but iron, in consequence of its atoms being more 

 closely packed than those of most substances, is probably 

 only a conspicuous instance of a general property of 

 matter, viz., that when any one of the forces of a 

 substance is disturbed, all its others are simultaneously 

 affected ; other bodies of high atomic number, such as 

 cobalt and nickel, would probably behave similarly. And 

 as our means of detecting effects are so very crude in 

 comparison with the degree of minuteness of molecular 

 changes, we rarely observe more than an extremely small 

 fraction of the results which occur. Heat, as well as light, 

 doubtless arrives at our earth from every one of the great 

 multitude of distant heavenly bodies, but we have only 

 yet detected it in a single instance. 2 



Different researches present every degree of difficulty, 

 depending upon the circumstances of the particular case ; 

 and discoveries are usually difficult in proportion to their 

 degrees of unripeness and of intrinsic importance, because 

 their unripeness is due to the undeveloped state of other 

 parts of science, and those of importance usually require 

 extensive research. The former obstacle is sometimes so 

 great, that until science has advanced in other departments 

 the expected discovery cannot be made. Newton attempted 

 to make his great discovery of the law of action of gravity 

 in the year 1666, but had to set his "calculations aside 

 until June 1682, when he heard, at a meeting of the Royal 



1 Chapter IV., p. 33. 2 Mr. Stone has detected heat from Arcturus. 



