THE LUNAR WORLD. 93 



receive and to interpret the undulations which are trans- 

 mitted through the air. On an airless globe our ears 

 would be almost useless ; we could hear no sound trans- 

 mitted as those sounds are which usually reach us. I ought, 

 however, to add that certain audible waves admit of being 

 transmitted through other materials besides air, and con- 

 sequently in some exceedingly imperfect and indirect 

 method a sense analogous to that possessed by our ears 

 might be rendered available on an airless globe. The 

 other sense which would be useless to any inhabitants who 

 might dwell on our satellite or other airless globe would 

 be that of smell. Although much less is known about 

 this sense than about either the sense of vision or that 

 of hearing, yet it seems certain that our nasal organs 

 receive extremely minute particles, and when these come 

 in contact with our olfactory nerves the sensation appro- 

 priate to those nerves is occasioned. Whatever may 

 be the mechanism of this process, it can hardly be doubted 

 that air is the vehicle by which these particles, so minute 

 and so imponderable as to elude entirely all our other 

 senses, are wafted from their source. The sense of smell 

 would apparently be impossible on an airless globe like 

 the moon. 



There is, however, another wholly different class of sen- 

 sations which would be experienced by a denizen of this 

 earth if he were translated to a small globe like the moon. 

 We must remember that in every fibre of our constitution 

 we have been specially adapted to the life on this 

 particular sphere. We have already seen how our senses 

 are adjusted in harmony with the particular atmosphere 

 with which the earth is surrounded : we have now to 



