SCIENTIFIC SUMMARY. 
169 
whilst under his direction, Mr. Stone was led to examine all the cases of 
supposed great proper motion in the Southern Stars of the British Association 
Catalogue. In the greater nupiber of cases they were found to arise from 
defective observations, but in some few cases they were confirmed. The most 
noteworthy instances were the group to which Mr. Stone has directed atten- 
tion. From a careful consideration of each case, Mr. Stone arrived at the 
following conclusions : : — 
That the four stars of the group under consideration have proper motions 
much larger than the average proper motions of stars. 
That the stars have a common proper motion of more than a second 
of arc. 
That each star of the group is moving away from every other star of the 
group, by quantities which are small compared with the common proper 
motion of the group. 
That, roughly speaking, the velocities of separation are larger, the larger 
the present angular separation of the stars. 
From these conclusions it seems probable that all these stars are slowly 
moving- away from one common point, so that many years back they were 
all very much closer to one another, and may have formed part of one com- 
mon star system. With the present rate of motion of separation it must 
have taken these stars over three million years to have moved to their present 
positions from a point where they would have been close together. Mr. 
Stone remarks that it appears to him that such a system as the present one 
may have originated from a system of stars like eq, and a 2 Centauri , which 
consists of two binary stars moving round each other, and with a large com- 
mon proper motion, having by reason of that larg-e common proper motion 
been brought sufficiently near to another binary double star to disturb the 
orbital motion of each and change the motion of each from closed to open 
orbits. The whole question opened by Mr. Stone is of the highest interest 
and deserves still further investigation, when the proper time arrives. 
The Nebula in the Pleiades. — Some twenty years ago, Temple, whilst at 
Venice, discovered, with a 4-inch telescope, a fine, bright nebula close to the 
bright star Merope in the Pleiades. It was elliptical in form and covered an area 
of nearly a fifth of a square degree. Temple showed it to Valz and other astrono- 
mers, and it was seen by Peters -with the 8-inch equatorial of the Altona Obser- 
vatory . Subsequently it was looked for by other observers either without success, 
or else seen as a very faint, indistinct object. Even Temple, though it is true 
with another instrument and in another locality, describes it as being far 
less distinct than when first seen. Subsequently, when observing near 
Florence with larger instruments, Temple saw the nebula as large and 
as bright as ever. Prof. Schiaparelli of Milan also observed it with the 
fine refractor at Milan, and describes it as bright and distinct, and com- 
pletely surrounding the star Merope , whilst outlying portions seemed to 
extend as far as Plectra. Schiaparelli remarks : 1 It is singular that so many 
persons should have examined the Pleiades without paying attention to this 
great nebula, which nevertheless is so evident an object on a clear sky.’ 
Maxwell Hall, in Jamaica, also found the nebula very bright with a 4-inch 
telescope, and shows it as nearly half a square degree in area. Several 
astronomers came to the conclusion that the nebula was variable. Others 
