448 FIRST REPORT UPON MAGNETIC WORK

believed that the best results possible under the conditions imposed
have been obtained.

Some objections might be raised to the method of reducing each
magnetic element to its particular daily mean. Now the mean decli-
nation takes place at a certain instant or instants, the mean inclination
at other times, and the mean horizontal intensity at still another time
during the day. And yet the method of discussion would lead one
to suppose that they all referred to the same instant of time. When
we combine three such mean quantities the resulting vector cannot
be physically interpreted; we are combining quantities that really
do not belong together, but this is a matter that need not concern us
at the present moment.

No fixed order was followed in making the entire set of obser-
vations. It was believed that the utmost freedom in this regard
would be most conducive to success. The order followed at any
particular station was controlled by the conditions prevailing at the
time. When possible, the endeavor was made to follow that par-
ticular order which at the time of day when the observations were
made would give the best results for each element.

It is not possible to describe in detail in this paper the methods of
observation employed for dip and intensity. Essentially the same
methods in general use were adopted. Absolute observations of the
intensity were made at each station. By means of the observations
made from time to time at the base station it will be possible likewise
to treat each set of intensity observations—deflections and oscillations
—separately and thus the two results may be compared. The deflec-
tion experiments were frequently made with two distances, so that
the distribution coefficient can be determined from a large number
of field observations. In the dip observations the polarity of the
needle was reversed at every station. At the beginning of the work
two different dip needles were used and the dip determined independ-
ently with each. The results with Needle No. II exhibiting decided
peculiarities, it was subjected to an examination and the pivots found
to be imperfect. I therefore worked entirely with Needle No. I,