and the Luminiferous Ether. 127 
The heading of the columns in the table gives the direction 
toward which the telescope pointe 
The footing of the erroneous column is marked x, and in the 
calculations the mean of the two adieasts foaynes is sub- 
stituted. 
The numbers in the columns are the positions e the center 
of the dark fringe in twelfths of the distance between the 
fringes. 
In the first two series, when the footings of the columns N. 
and S. exceed those of columns KH. an , the excess is called 
positive. The excess of the footings of N. “4, OVEF. 
‘those of N.W., S.E., are also called positive. “Tn the third 
and fourth series this is reverse 
e numbers marked “ excess” are the sums of ten observa- 
tions. Dividing therefore by 10, to obtain the mean, and also 
by 12 (since the numbers are twelfths of the distance between 
the fringes), we find for 
N.S. N.E., S.W. 
Sere foo +0°017 ‘050 
2 2 -...—0°025 —0°033 
ss k, Maun ieenaivaaneg tes +0°030 +0°030 
Bead oe ce Ue +0°087 
4 J 0-089 07137 
Mean +0°022 + 0°034 
The displacement is, therefore, 
Tn favor of the columns NM. eu eee ng +0°022 
RO BW ee +0°034 
The former is too small to be considered as showing a dis- 
placement due to the simple change in direction, and the latter 
should have been zero. 
he numbers are simply outstanding errors of experiment. 
It is, in fact, to be seen from the footings of the columns, that 
the numbers increase (or decrease) wit] more or less regularity 
from left to right. 
This gradual change, which should not in the least affect the 
periodic variation for which we are searching, would of itself 
necessitate an outstanding error, simply because the sum of the 
two columns farther to the left must ‘be less (or greater) than 
the sum of those farther to the ee 
This view is amply confirmed by the fact that where the ex- 
cess is positive for the column N.S,, it is also positive for N.E., 
S.W., and where negative, negative. If, therefore, we can. 
prea ase this gradual change, we may expect a much smaller 
error, This is most readily accomplished as follow 
dding together all the footings of the four rae the third 
and foutth with negative sign, we obtain 
N. N.E. EK. 8.K. 8. S.W. Ww. N.W. 
305. BES 960 = kOe ee 
