106 - BR. W. McFarland—Perihelion and Eccentricity. 
in Mr. Croll’s ‘ Climate and Time,” and also by those given in 
Mr. Stockwell’s pamphlet on the “ Secular Equations of the 
Moon’s Mean Motion.” The constants of the latter formule 
differ slightly from those found for the sun’s increased parallax 
in the xviiith vol. of the Smithsonian Contributions. 
An inspection of the table shows that the motion of the peri- 
helion is exceedingly irregular, _ tesigpscyan retrograde. 
The intervals between the maximum and minimum points 
in the curve of eccentricity also earn greatly, as a glance at the 
chart will show. The initial periods, 1800 and 1850, for the 
two sets of formule, differ so little from each other that the 
ordinates to the curves practically coincide. 
One object of the table is a comparison of the results reached 
by these two sets of formule. It is obvious that great changes 
in the eccentricity will occur, unless the elements of distu urb- 
ance reduce more nearly to zero than is probable, or perhaps 
ossible. 
: The chart also shows that the time, rather than the value of 
the maximum ica ip varies ; but even this variation of 
the time, as shown e two series of values, is not great 
when long periods are aan 
Mr. Stockwell’s formule are deemed the more accurate, yet 
the two curves exhibit a general conformity throughout their 
whole extent. Whether a period of high eanteaty occurred 
about 800,000 years ago, or 700,000, is a small matter :—the 
It is regretted that it has been necessa ary to draw the 
curves on so small a scale. “Whea drawn large they move on 
with a generous sweep, so to speak, and make no sharp turns. 
The co apehane having been made in the small intervals at 
it big amid the press of onerous duties, errors may have bee 
and remained undetected; but it is thought that shiecs 
are none of sufficient mag nitade to vary the general results to 
any considerable amou 
The computations were originally begun at the instance of 
President Orton, of the Ohio State University, and were con- 
tinued, I ma be permitted to say, on the ——e of Mr. 
James ‘Croll, of the Geological Survey of Sco 
It is scarcely necessary to add that if whys one wishes to 
determine the difference between the greatest and least dis- 
tance of the sun, it is only necessary ‘to multiply the sun’s 
mean distance by” twice the eccentricity. 
Ohio State University, June 3, 1880. 
