SOLAR, AND STELLAR PROPER MOTIONS. 
147 
Halley’s paper was not only the first, but for twenty years 
it was the only publication in regard to the new hypoth¬ 
esis. At that time, communication between widely separated 
astronomers was very tedious, and new departures from the 
beaten tracks of accepted theories were subject to grave 
doubts, and frequently to harsh criticisms. 
On November 12th 1738, Jacques Cassini 2 presented a 
paper to the Royal Academy of Sciences at Paris, on “ The 
variations observed in the situation and motion of several 
fixed stars.” The author announced that the earliest work of 
the Royal Observatory at Paris was the examination of a num¬ 
ber of the stars catalogued by Ptolemy, and especially those 
cited by Halley, in order to test the hypothesis of stellar 
proper motion. His comparisons with ancient results proved 
conclusively to his mind, that certain stars had moved from 
their former positions, while other stars of equal magnitude 
gave no evidence of abnormal change. As a result of his 
investigations, he concluded that the stars with proper mo¬ 
tion probably revolved about some center, situated perhaps 
beyond our perception, and remarked, finally: ‘ It results 
from this hypothesis that, following the several positions of 
these stars in their orbits, some would appear to move in 
longitude from west to east, others in the opposite direction, 
others, finally, would appear to approach or to recede from 
the pole of the ecliptic in accordance with observations. 
Be that as it may, it must remain certain that although 
the greater part of the stars maintain the same positions 
among themselves, there are some that approach or recede 
from each other, in longitude as well as in latitude, which 
is, as we have already remarked, very important to recog¬ 
nize for the progress of Astronomy since it is principally 
to the fixed stars that we refer the movements of the other 
celestial bodies.’ 
All the discussions and investigations of proper motion 
for the next forty years were of the same general character 
2 Cassini, Jacques. Histoire de l’Academie Royale des Sciences. Paris, 
1738; 331. 
