to the Legislature of the State of New York. 265 
render it visible, and another to keep in the line of observation and 
to mark the point where it terminates. 
The usual means should be employed to ascertain the fact that 
there is nothing about the place by which the needle may be at- 
tracted. 
Within the limits of the State of New York, the following nti 
is practicable, and, if carefully conducted, will give a meridian as 
true, for the present purpose, as can be expected from the other 
prescribed methods. 
Alioth and Gamma Cassiopeia pass the meridian at the same 
moment, within two seconds of time, the one below and the other 
above the pole. If then the line be accurately observed in which 
they appear when in the same vertical, that line will be the true me- 
ridian, without an appreciable error; and as the difference between 
the changes in right ascension of these two stars is only 13 hun- 
dredths of a second annually, it will not sensibly affect the accuracy 
of the rule and its practical results for many years. 
At some distance beyond our north bounds these stars will so 
nearly approach the zenith as to render the observation inconvenient, 
with a plumb line, but not with a transit instrument at any place far- 
ther to the north. ‘The observation will be practicable either way, 
as far south as the 35th degree of north latitude, whence Gamma 
Cass. will be seen at its lowest depression, somewhat less than five 
degrees above the horizon. In latitude 43°, Alioth will come with- 
in 14 degrees of the zenith, and Gamma Cass. within 13 degrees of 
the horizon, at the time when the observation is recommended to be 
made, which is from the middle of May to the Ist of June. On the 
15th of May, the stars will be on the meridian at about 19 minutes after 
9 o’clock in the evening, apparent time, and about four minutes ear- 
lier on every succeeding day. 
Gamma is the middlemost of the bright stars that compose Cas- 
_ Slopeia’s chair. 
The meridian line being thus accurately and permanently fixed, 
(and this ought to be considered as an indispensable appendage to 
every college and academy,) observations should be made on it at 
least once in every year, in order to ascertain the difference between 
it and the magnetic meridian. For the sake of uniformity, let this 
be done in October. 
These observations should be made early in the morning, for it 
is well known that the varmtion of the needle will be increased, 
Vou. XXV.—No. 2. 
