A SOUTHERN OBSERVATORY. 123 
instrumental, causes of error. Accuracy is indeed arduous; and the 
astronomer who is not what the old Romans used, in their grand way, 
to look down upon as a cumini sector, had better learn another profes- 
sion. 
Twenty-seven stars in the southern hemisphere are now being, or are 
about to be, measured for parallax with the Cape heliometer. Their 
selection was governed by the ultimate object of gathering information 
as to the scale and plan of the marvellous aggregation of suns to which 
our sun belongs, and amidst which it is moving, in an unknown orbit, 
to meet unknown destinies. For this purpose, facts of two kinds are 
urgently needed—facts relative to the real distribution, and facts relative 
to the real movements of the stars in space. Dr. Gill’s operations, when 
completed, can not fail to bring important reinforcements to our present 
small store of each. 
Ten stars of the first magnitude lie to the south of the celestial equa- 
tor, of which nine (Alpha Centauri being already safely disposed of) 
are in course of measurement at intervals of six months. The upshot 
will be to give the average distance corresponding to the first order of 
stellar brightness in the southern hemisphere. An analogous result 
has lately been published by Dr. Elkin for the ten chief northern lumi- 
naries. Their distance, “all round,” proves to be thirty-six “light- 
years.” That is to say, light from their photospheres affects our senses 
only after our planet has revolved, on an average, thirty-six times in 
its orbit round the sun. So that all our knowledge, even of the stars 
presumably nearest to the earth, refers, in thisyear 1889, to the “mean 
epoch” 1853. We shall learn presently whether the ‘‘ mean epoch” for 
the southern bright stars corresponds approximately to this date, or 
whether a marked disparity may countenance the surmise of our eccen- 
tric situation in the group of luminaries to which our sun more espe- 
cially belongs. 
Dr. Gill’s list includes five second magnitude stars, the annual per- 
spective displacements of which (if large enough to be measurable) will 
give something like a definite scale of increasing distance with de- 
creasing luster. A conclusion will then be feasible as to the rate of 
movement of the sun in space. The elder Struve made it about 5 miles 
a second, but on the supposition of the brightest stars being between 
two and three times nearer to us than they seem really to be. We can 
now see that the actualspeed of the solar system can scarcely fall short 
of 12, or exceed 20 miles, a second. By a moderate estimate, then, our 
position in space is changing to the extent of 500,000,000 of miles annu- 
ally, and a collision between our sun and the nearest fixed star would 
be inevitable (were our course directed in a straight line toward it) after 
the lapse of fifty thousand years! 
The old problem of ‘ how the heavens move,” successfully attacked 
in the solar system, has retreated to a stronghold among the stars, from 
which it will be difficult to dislodge it. In the stupendous mechanism 
of the sidereal universe, the acting forces can only betray themselves to 
