THE SUN’S MOTION IN SPACE. 111 
number of partial systems is more than probable; but the inconceiva- 
ble leisureliness with which their mutual relations develop renders the 
harmony of those relations inappreciable by short-lived terrestrial 
denizens. ‘ Proper motions,” if this be so, are of a subordinate kind; 
they are indexes simply to the mechanism of particular aggregations, 
and have no definable connection with the mechanism of the whole. 
No considerable error may then be involved in treating them, for pur- 
poses of calculation, as indifferently directed; and the elicited solar 
movement may genuinely represent the displacement of our system rela- 
tive to its more immediate stellar environment. This is perhaps the ut- 
most to be hoped for until sidereal astronomy has reached another sta- 
dium of progress, unless, indeed, effect should be given to Clerk Max- 
well’s suggestion for deriving the absolute longitude of the solar apex 
from observations of the eclipses of Jupiter’s satellites (Proc. Roy. Soc., 
vol. Xxx, p. 109). But this is far from likely. In the first place, the 
revolutions of the Jovian system can not be predicted with anything 
like the required accuracy. In the second place, there is no certainty 
that the postulated phenomena have any real existence. If however 
it be safe to assume that the solar systein, cutting its way through 
space, virtually raises an :etherial counter-current, and if it be further 
granted that light travels faster with than against such a current, then 
indeed it becomes speculatively possible, through slight alternate accel- 
erations and retardations of eclipses taking place, respectively, ahead 
of and in the wake of the sun, to determine his absolute path in space 
as projected upon the ecliptic. That is to say, the longitude of the 
apex could be deduced together with the resolved part of the solar 
velocity; the latitude of the apex, as well as the component of velocity 
perpendicular to the plane of the ecliptic, remaining however unknown. 
The beaten track, meanwhile, has conducted two recent inquirers to 
results of some interest. The chief aim of each was the detection of 
systematic peculiarities in the motions of stellar assemblages after the 
subtraction from them of their common perspective element. By vary- 
ing the materials and method of analysis, Prof. Lewis Boss, director of 
the Albany Observatory, hopes that corresponding variations in the 
upshot may betray a significant character. Thus, if stars selected on 
different principles give notably and consistently different results, the 
cause of the difference may, with some show of reason, be supposed to 
reside in specialties of movement appertaining to the several groups. 
Prof. Boss broke ground in this direction by investigating 284 proper 
motions, few of which had been similarly employed before (Astr. Jowr., 
No. 213). They were all taken from an equatorial zone 4° 20’ in breadth, 
with a mean declination of +3°, observed at Albany for the catalogue 
of the Astronomische Gesellschaft, and furnished data accordingly for 
a virtually independent research of ‘a somewhat distinctive kind. It 
ras carried out to three separate conclusions. Setting aside five stars 
with secular movements ranging above 100°, Prof, Boss divided the 
