54 Mare Vaporum and the Lunar Clefts. 



of minute craters, with a lateral communication throughout : 

 on the other hand, there are regions where contiguous moun- 

 tains form, with their straight and parallel sides, gorges much 

 resembling these clefts, and where long straight valleys are 

 distinguished from them chiefly by their greater proportional 

 breadth and inferior steepness ; and several valleys of this 

 kind are to be met with in the immediate neighbourhood of 

 true clefts, and parallel to them. From these and other indi- 

 cations, such as their want of connection with any definite 

 object, their occasional repetition in parallel lines within a 

 small distance, and more especially their magnitude (as Schr. 

 had already perceived), the idea of an artificial origin must be 

 aid aside. 



On this subject B. and M. have some remarks, which, 

 though referring to speculations which have never found great 

 favour among ourselves, are still worthy of consideration. They 

 observe that, but from inattention to the scale of the objects we 

 are studying, and from the unreasonable expectations enter- 

 tained at the end of the last century of a marvellous increase 

 of magnifying power (some persons, in Germany we may pre- 

 sume, seem to have been anticipating the use of powers of 

 15,000 !), the idea of these clefts being lines of road, or any- 

 thing else of an artificial nature, would never have been 

 seriously entertained.* In all such analogies, they judiciously 

 remark, one very important point has been ignored — the 

 relative proportion of gravity on the different bodies of the 

 system. When this, as on the Moon, is 6f times inferior to 

 that on the Earth, fresh relations are introduced between 

 power, weight, and motion; and while we have no positive 

 information as to artificial products on the Moon, it may be 

 maintained with great probability that they would be totally 

 unlike our own, and that, even if our optical means were 

 capable of reaching them, they would not appear in any 

 recognized or familiar form. Remarks of this kind are valu- 

 able if they check the vagaries of irrational fancy. We should 

 take care, however, not to push them too far; it would be 

 possible, though much less probable, to err in an opposite 

 direction, and to impede the progress of discovery by an over- 

 weening estimate of our own previous conclusions. 



The hypothesis of their being actually existing or dried-up 

 water-courses may be disposed of with little trouble. All 

 modern observers are agreed as to the absence of water, at 

 least in any noticeable quantity, from the Moon as it now is ; 

 but could we conceive, with Gruithuisen, that it had formerly 



* Gruithuisen referred them partly to dried river-heds, or natural clefts, partly 

 to artificial clearings through forest lands, used in either case as lines of 

 communication. 



