SCIENTIFIC USE OF THE IMAGINATION 137 



its present form; that as the ages rolled away, heat was 

 wasted, condensation followed, planets were detached; 

 and that finally the chief portion of the hot cloud reached, 

 by self-compression, the magnitude and density of our 

 sun. The earth itself offers evidence of a fiery origin; 

 and in our day the hypothesis of Kant and Laplace re- 

 ceives the independent countenance of spectrum analysis, 

 which proves the same substances to be common to the 

 earth and sun. 



Accepting some such view of the construction of our 

 system as probable, a desire immediately arises to con- 

 nect the present life of our planet with the past. We 

 wish to know something of our remotest ancestry. On 

 its first detachment from the central mass, life, as we 

 understand it, could not have been present on the earth. 

 How, then, did it come there ? The thing to be encour- 

 aged here is a reverent freedom — a freedom preceded by 

 the hard discipline which checks licentiousness in specula- 

 tion — while the thmg to be repressed, both in science and 

 out of it, is dogmatism. And here I am in the hands of 

 the meeting — willing to end, but ready to go on. I have 

 no right to intrude upon you, unasked, the unformed no- 

 tions which are floating like clouds, or gathering to more 

 solid consistency, in the modern speculative scientific 

 mind. But if you wish me to speak plainly, honestly 

 and undisputatiously, I am willing to do so. On the 

 present occasion — 



You are ordained to call, and I to come. 



"Well, your answer is given, and I obey your call. 

 Two or three years ago, in an ancient London college, 

 I listened to a discussion at the end of a lecture by a very 



