CONDITION OF THE LARGER PLANETS. 179 



enable us to discover such truths. The mere observer 

 who argues that observation and not reasoning is real 

 science, may be compared to an organ-blower who 

 should argue that his work, not that of the organist, 

 constituted real music. The organist cannot play 

 without wind, the manufacturer cannot get on without 

 raw materials, and in like manner, Kepler would never 

 have established his laws without the observations 

 collected by Tycho Brahe, nor would Newton have 

 discovered the law of gravity without the raw material 

 collected by Flamstead ; but as it is important in 

 organ music that the wind be exhausted in melody, 

 not in mere noise, and important in manufacture that 

 the raw material be employed to make useful not 

 useless articles, so it is and has been a matter of 

 considerable importance whether observations have 

 been idly worked up in false systems like those of 

 Ptolemy or Descartes, or wisely used to ascertain the 

 truth, as by Copernicus, Kepler, or Newton. 



The theory which is now to be considered is this, 

 that the planets Jupiter and Saturn are still in a state 

 of intense heat, being at a much earlier stage of 

 planetary development than our earth or those four 

 companion orbs, Mercury, Venus, Mars, and the moon 

 (in one sense more specially a companion than the 

 others), which have been called the terrestrial planets. 



At the outset it may be well to consider the 

 evidence for the only other theory which has been 

 advanced on the subject the theory commonly accepted 

 with apparently as little question as though it had 



K 2 



