SYSTEM OF OBSERVATION, AND PERSONAL ESTABLISHMENT. xi 
D, The Declinometer. 
t, Its Reading Telescope. 
A, The Azimuth Circle and Transit. 
H, The Bifilar or Horizontal Force Magnetometer. 
t’, Its Reading Telescope. 
P, A Pillar for a Collimator (not used). 
V, The Balance or Vertical Force Magnetometer. 
I, The Inclinometer. 
B, The Standard Barometer. 
W, The Anemometer. 
W’, The Wind Vane Dial-Plate. 
T, The Thermometer Case. 
C, The Mean Time Clock. 
S, The Copper Stove. 
ns, The Astronomical Meridian. 
Dt, The Magnetical Meridian. 
The two vanes to the right in the elevation are those for the direction and 
force of the wind ; the other two were added after 1843. 
§ 2. SysTEM OF OBSERVATION, AND PERSONAL ESTABLISHMENT. 
5. The system of observation followed in 1841 and 1842 consisted of four 
daily observations of the magnetical and meteorological instruments, at the hours 
of 8 and 11 a.M., and 2 and 5 p.m., hours recommended by Dr Luoyp for one per- 
manent observer ;* of term observations, made once a month for 24 hours; of 
observations of magnetic dip ; and of extra magnetical observations, made during 
marked magnetic disturbances. The personal establishment in 1841 and 1842 con- 
sisted of one permanent observer, and three assistants on term-days. It seemed 
desirable to render the daily observations somewhat more complete; and as this 
would also necessarily entail a greater amount of labour in reductions, Sir Tuomas 
_ BRIsBANE, on my suggestion, through Professor Forses, and with his advice, added 
another permanent observer to the establishment. Mr JoHn WELSH, a student in 
_ Arts of the Edinburgh University, was appointed in the end of December 1842. 
_ The term-assistants in 1843 were Messrs Hoce and Dons, who assisted in the pre- 
vious year. In 1843, the daily observations were made at every even hour of Got- 
tingen mean time, from 6 a.m. till 10 P.M., or at every two hours, from 5" 10™ a.m. 
till 9° 10" p.m., Makerstoun mean time. The other observations consisted of term- 
* The observer had also the charge of a Transit Instrument, and of several Sidereal Clocks, which 
__were compared daily. 
