1874.] and its Influence on Lunar Questions. 503 
observations ; but they cannot be considered as disturbing 
the explanation that the cause of the phenomena in question 
is simply the known irregularities on the surface, which also 
accounts for the observations, although not so well. It is, 
however, too generally considered that the possibility of two 
explanations of one circumstance weakens the probability of 
both. 
Competent dealing with the problem of the physical 
condition of the surface of the moon requires a special 
knowledge of the minuter details of the lunar surface, rarely 
met with in combination with a proper acquaintance with 
the more theoretical elements involved in the subject, and, in 
consequence, questions have often been considered as 
standing in a different position to their real nature. A mere 
general familiarity with the principal configuration of the 
moon’s surface and the phenomena to be seen is not sufficient 
in the hands of the most able theorist for the proper con- 
sideration of the complex problems involved, and it is not 
strange if the resulting conclusions are often not all that 
could be desired. 
The study of the details of the moon’s surface, until very 
recently long left in the hands of a very few indefatigable 
astronomers, from the interest inseparable from it is now 
attracting the more general attention it demands, and gives 
promise of before long placing us in a more satisfactory 
position with regard to the nature of the lunardetails. The 
admirable work of Beer and Madler, so far from being 
exhaustive as was long thought, brought us to only the 
threshold: Schmidt’s forty years’ work, gigantic as are the 
results, only reaches the minutiz, and will require years of 
revision; while the real character of the objects now known 
to exist merely, is nearly untouched ground, and it is there 
where some of the greatest difficulties will be felt, for to 
evolve a theory as to their source is far different from 
detecting their true origin. But there is promise ere many 
years are over that we may be in possession of a sufficiency 
of exact knowledge of the features presented by the moon to 
enable some more satisfactory conclusions to be drawn as to 
the events of the past history, present condition, and 
immediate future of our satellite. 
