Mar. 12, 1874J 



NATURE 



359 



Next, after the tremendous evidence of vulcanicity 

 afforded by the craters and walled plains, come the 

 bright streaks which have ever been a puzzle to observers. 

 These are seen under various illuminations to radiate 

 from several craters for hundreds of miles. Here I will 

 quote from the book, p. 133 : — 



" There are several prominent examples of these bright 

 streak systems upon the visible hemisphere of the moon ; 

 the focal craters of the most conspicuous are Tycho, 

 Copernicus, Kepler, Aristarchus, Menelaus, and Proclus. 

 Generally, these focal craters have ramparts and interiors 



distinguished by the same peculiar bright or highly re- 

 flective material which shows itself with such remark- 

 able brilliance, especially at full moon ; under other coHr 

 ditions of illumination they are not so strikingly visible. 

 At or nearly full moon, the streaks are seen to traverse 

 over plains, mountains, craters, and all asperities ; 

 holding tlieir way totally disregardful of every ob- 

 ject that happens to lie in their course. The most 

 remarkable bright streak system is that diverging from 

 the great crater Tycho. The streaks that can be easily 

 individualised in this group number more than one 

 hundred, while the courses of some of them may be 



-Second stage, 



traced through upwards of six hundred miles from their 

 centre of divergence. Those around Copernicus, although 

 less remarkable in regard to their extent than those 

 diverging from Tycho, are nevertheless in many respects 

 well deserving of careful examination ; they are so nume- 

 rous as utterly to defy attempts to count them, while their 

 intricate reticulation renders any endeavour to delineate 

 their arrangement equally hopeless." 



Ouite different from these radiating streaks are very 



definite "cracks," some of which are easily seen with 

 moderate telescopic powers. There are, hov/ever, a very 

 large number recorded, some of which are excessively 

 delicate objects. 



Last among exceptional phenomena to be recorded is 

 the circumstance that our satellite has no atmosphere to 

 speak of : no clouds, no fogs have ever been seen on the 

 moon as on Mars, while no effects have been produced 



Fig. 3.— Thu-d 



at occultations of stars and planets by the moon such as 

 should be produced did an atmosphere in any way com- 

 parable to our own exist on our satellite. 



Although the most important part of the text consists 

 of an attempted explanation of all but the atmospheric 

 phenomena, much of it deals, and in a very admirable 

 way, with lunar topography, a perusal of which will be 

 desirable before the discussion is taken up, in the case, 



at all events, of those unfamiliar with the moon's surface. 

 The consideration of the various questions involved is 

 preceded by chapters on the cosmical origin of our system 

 and the genLration of heat, the result of which was that 

 at one time the moon was an incandescent sphere with 

 a cooling crust, and even then if I understand the authors, 

 there was no lunar atmosphere (p. 1 7), for they give an 

 answer, or think they do, in this sense to the question 



