1873O Condition of the Moon's Surface. 29 



valueless and closed, which could quadruple that yield if it 

 were shown that a 20-dollar ore could be mined to a profit. 

 Several English companies are now entering on active 

 mining operations in Gilpin County, and it is to be hoped 

 they will inaugurate a new system. This they are the more 

 likely to do, as the properties they have purchased are not 

 hampered with old stamp mills. 



III. CONDITION OF THE MOON'S SURFACE. 



By Richard A. Proctor, B.A. (Cambridge), 

 Honorary Secretary of the Royal Astronomical Society. 



the study of our earth's crust — or the science of 

 Geology — is capable of throwing some degree of light 

 on the past condition of other members of the solar 

 system, the study of those other orbs seems capable of at 

 least suggesting useful ideas concerning the past condition 

 of our earth. There are members of the solar system 

 respecting which it may reasonably be inferred that they 

 are in an earlier stage of their existence than the earth. 

 Jupiter and Saturn, for instance, would seem — so far as ob- 

 servation has extended — to be still in a condition of intense 

 heat, and still the seat of forces such as were once probably 

 at work within our earth. We see these planets enwrapped, 

 to all appearance, within a double or triple coating of clouds, 

 and we are compelled to infer, from the behaviour of these 

 clouds, that they are generated by forces belonging to the 

 orb which they envelope ; we have, also, every reason which 

 the nature of the case can afford to suppose that our own 

 earth was once similarly cloud-enveloped. We can scarcely 

 imagine that in the long-past ages, when the igneous rocks 

 were in the primary stages of their existence, the air was 

 not loaded heavily with clouds. We may, then, regard 

 Jupiter and Saturn as to some degree indicating the state of 

 our own earth at a long-past epoch of her existence. On the 

 other hand, it has been held, and not without some degree 

 of evidence in favour of the theory, that in our moon we 

 have a picture of our earth as she will be at some far-distant 

 future date, when her period of rotation has been forced 

 into accordance with the period of the moon's revolution 

 round the earth, when the internal heat of the earth's globe 



