314 The American Geologist. November, 1904. 
higher latitudes. '\\'e shall see what the oscillation proves 
regarding this matter. 
It is a known fact, that the active condition and erup- 
tions of the Sun are varying. Now, since the radiation of 
light is of a certain periodicity and oscillates between maxi- 
mum and minimum, it follows that for the same rieason the. 
light-stuff around the Earth is of oscillating density; and 
the moon in consequence, meets with an oscillating resist- 
ing force. It is remarkable, indeed, to notice that the oscil- 
lation of the lunar orbit stands in very close relation to the 
oscillation of this resisting force, and in a degree which 
seems to answer perfectly to the richness of the light-stuff 
whjch causes the resistance. By comparing the varying in- 
clination of the lunar orbit to the ecliptic, as it is indicated 
in the ephemerides, with several succeeding maxima and 
minima of the Sun's varying activity during the same period, 
we come in possession of the necessary data, which throw 
light on this subject. 
The Sun's activity was at maximum, for instance, in and 
about 1870; we may count it a period of three years. The 
following minimum occurred in and about 1876. The next 
maximum rose high in 1880, but covered at that time a long- 
er period than in the 70's. Eruptions of the Sun to the 
hight of from 100,000 to 400,000 kilometers were observed 
during this maximum for several years. The following min- 
imum occurred in 1887: but this minimum did not fall as low 
as the foregoing one, which is generally the case with a 
minimum following a high maximum. Thereupon a maxi- 
mum again began to appear, which reached its culmination in 
1892. This is well known to astronomers, and not least from 
the extent of the Sun's corona at the time of the eclipses 
during that period. 
Let us now compare these maxima and minima with the 
oscillation of the lunar orbit during the same period, and 
see if we can find their reciprocal relations. 
The inclination of the lunar orbit to the ecliptic, which we 
have above indicated as varying between 4° 57' and 5° 19', 
fell during the maximum activity of the Sun in Xovember, 
1868, only to 5° o' 5", as its minimum, and rose in February 
the following year to 5° 17' 54". This was the highest mini- 
