to the Legislature of the State of New York. 261 
According to Dr. Brewster’s formula for finding the mean tempe- 
rature of a place, that of Albany is 50°3191°. 
The Regents, sensible of the value to science and to the whole 
landed interest of the State, of a record of the variations of the nee- 
dle from year to year, have addressed a circular to the Colleges and 
Academies, requesting them to make observations upon this. poin 
and to attain accuracy and uniformity in the results, the Chancellor 
has furnished a formula for establishing a true meridian, and the most 
important particulars to be regarded in observing, between it and the 
magnetic meridian. 
This circular being drawn up with great judgment and ability, and 
being of general as well as local interest, we now republish, as being 
the most effectual mode of expressing, at once, our good will to the 
very important object i in view, and of giving the circular the range of 
this Journal. 
_ An indispensable prerequisite is to have a true meridian establish- 
ed, indicated by fixed and permanent monuments. The manner in 
which this is to be done, in order that it may be accurately establish- 
ed, requires special directions. 
In years past, a rule has been seeientivad for obtaining an approx- 
imate meridian, supposed sufficient for common purposes; that is, 
to take the direction of the pole star when it is in the same vertical 
or perpendicular line with epsilon urse majoris, called Alioth, that 
is, the first star in the tail of the Great Bear, or the one next to the 
four most conspicuous in that constellation. This rule was once 
correct, but it is more than a century past: since that, the interval 
between the time when these two stars are in the same vertical, and 
the time when the pole star is in the meridian, has been gradually 
increasing, on account of the greater annual increase of the right 
ascension of the pole star than that of Alioth. Still some, not aware 
of this fact, have continued to prescribe the ancient rule. Others 
have calculated the interval for a certain period of time, without ad- 
verting to the changes which would occur in succeeding periods. 
In order to practice on this rule with accuracy, calculations must be 
made for the time when it is adopted, and for this purpose the fol- 
lowing formula is given as an example, adapted to the beginning of 
this year and a medium latitude, which will give a result sufficiently 
accurate for every part of our state, and which may be adopted in 
practice without producing a sensible error for several years, for the 
purpose now contemplated. 
