240 THE BORDERLAND OF SCIENCE. 



hot matter within is seen to be in a state of seething 

 activity, and a considerable quantity exudes from the 

 opening. If a bogie filled with fused cinder is left 

 undisturbed, a veritable spontaneous volcanic eruption 

 takes place through some portion, generally near the 

 centre, of the solid crust. In some cases, this eruption 

 is sufficiently violent to eject small spurts of molten 

 cinder to a height equal to four or five times the width 

 of the bogie. The crust once broken, a regular crater 

 is rapidly formed, and miniature streams of lava 

 continue to pour from it ; sometimes slowly and regu- 

 larly, occasionally with jerks and spurts, due to the 

 bursting of bubbles of gas. The accumulation of these 

 lava-streams forms a regular cone, the height of which 

 goes on increasing. I have seen a bogie about ten or 

 twelve inches in diameter, and nine or ten inches deep, 

 surmounted in this way by a cone about five inches 

 high, with a base equal to the whole width of the 

 bogie. These cones and craters could be but little 

 improved by a modeller desiring to represent a 

 typical volcano in eruption. 9 



The aspect of the moon's crater-covered surface cer- 

 tainly accords better with the supposition that active 

 processes like those described by Mr. Williams were in 

 operation when that surface was formed, than with the 

 theory that slow and intermittent volcanic action like 

 that with which we are now familiar on earth, modelled 

 the moon's surface to its present configuration. In the 

 former case water would not have been needed, and 



