1816.) Dr. John Rolison. sol 
discovering ‘the general principle which is common to all these 
facts. LEven/a single experiment may be sufficient to prove a very 
general fact. When a guinea and a feather, let fall from the top of 
an exhausted receiver, descend to the bottom of it in the same 
time, it is very true that this only proves the fact of the equal acce- 
leration of falling bodies in the case of the two substances just 
named; but who doubts that the conclusion extends to all different 
degrees of weight, and that the uniform acceleration of falling 
bodies of every kind may safely be inferred. 
A society for the cultivation of literature and science had existed 
in Edinburgh ever since the year 1739, when, by the advice, and 
under the direction of Mr. Maclaurin, an association, formed some 
years before for the improvement of medicine and surgery, enlarged 
its plan, and assumed the name of the Philosophical Society. This 
Society, which had at different times reckoned among its members 
some of the first men of whom this country can boast, had pub- 
lished three volumes of memoirs, under the title of Physical and 
Literary Essays ; the last in 1756, from which time the Society had 
languished, and its meetings had become less frequent. At the 
time | am now speaking of it was beginning to revive, and its ten- 
dency to do so was not diminished by the acquisition of Mr. Robi- 
son, who became a member of it soon after his arrival. It had 
often occurred that a more regular form, and an incorporation by 
royal charter, might give more steadiness and vigour to the exer- 
tions of this learned body. In 1783, accordingly, under the 
auspices of the late excellent Principal of this University, a royal 
charter was obtained, appointing certain persons named in it as a 
new society, which, as its first act, united to itself the whole of the 
Philosophical. . 
Professor Robison, one of those named in the original charter, 
was immediately appointed Secretary, and continued to discharge 
the duties of that office till prevented by the state of his health 
several years after. 
The first volume of the Transactions of this Society contains the 
first paper which Professor Robison submitted to the public, a 
Determination of the Orbit and the Motion of the Georgium 
Sidus directly from Observations, read in March, 1786. ‘This 
planet had been observed by Dr. Herschell on March 18, 1781, 
and was the first in the long list of discoveries by which that excel- 
lent observer has for so many years continued to evrich the science 
of astronomy. Its great distance from the sun, and the slowness of 
its angular motion, which Jast amounts to little more than four 
degrees from one opposition to the next, made it difficult to deter- 
mine its orbit with tolerable accuracy, from an arch which did not 
yet exceed an eighteenth part of the whole orbit. This was an in- 
convenience which time would remedy; but impatience to arrive 
even at such an approximation as the facts known will afford is 
natural in such cases, and Professor Robison, as well as several 
other mathematicians, were not afraid to attempt the problem, even 
