50 SCIENCE IN SHORT CHAPTERS. 



this to the other world of sensations producible by the 

 vibratory movements of matter lying between those per- 

 ceptible by our organs of hearing and vision, then strain 

 your imagination to its cracking point, and you will still 

 fail to picture the wonderland in which the smallest of our 

 fellow-creatures may be living, moving, and having their 

 being. 



THE OKIGIN OF LUNAR VOLCANOES. 



MANY theoretical efforts, some of considerable violence, 

 have been made to reconcile the supposed physical contra- 

 diction presented by the great magnitude and area of former 

 volcanic activity of the Moon, and the present absence of 

 water on its surface. So long as we accept the generally 

 received belief that water is a necessary agent in the evolu- 

 tion of volcanic forces, the difficulties presented by the lunar 

 surface are rather increased than diminished by further 

 examination and speculation. 



We know that the lava, scoriae, dust and other products 

 of volcanic action on this earth are mainly composed of 

 mixed silicates those of alumina and lime preponderating. 

 When we consider that the solid crust of the Earth is chiefly 

 composed of silicic acid, and of basic oxides and carbonates 

 which combine with silicic acid when heated, a natural ne- 

 cessity for such a composition of volcanic products becomes 

 evident. 



If the Moon is composed of similar materials to those 

 of the Earth, the fusion of its crust must produce similar 

 compounds, as they are formed independently of any atmos- 

 pheric or aqueous agency. 



This being the case, the phenomena presented by the 

 cooling of fused masses of mixed silicates in the absence of 

 water become very interesting. Opportunities of studying 

 such phenomena are offered at our great iron-works, where 

 fused masses of iron cinder, composed mainly of mixed 

 silicates, are continually to be seen in the process of cooling 

 under a variety of circumstances, 



