224 
Instruments at the Observatory. 
The usual method of observation is, with the instru¬ 
ment in the plane of the magnetic meridian ; but, for the 
purpose of testing the axles of the needles and the gra¬ 
duated circle of the instrument, observations are made as 
described in 5 and 6, occasionally. 
The foregoing description includes all the magnetical 
apparatus of an Observatory. 
For the mathematical skill and ingenuity shown in 
devising the Horizontal Force instrument, the scien¬ 
tific world is indebted to Professor Gauss, of the 
University of Gottingen ; and for the elegant little ap¬ 
paratus described as the Vertical Force Magnetometer, 
to Professor Lloyd, of the University of Dublin, from 
whose reports the abridged descriptions of these instru¬ 
ments contained in this paper have been principally 
collated. Besides these, the observatories are furnisned 
with a complete set of the most refined meteorological 
instruments for accurate observation of the atmospheric 
changes, in conjunction with the magnetical observations, 
a Transit Instrument for the correct determination of 
time, chronometers, &c. &c. 
Addition to Art. II. (See p. 189.) 
Notes on a Kangaroo Rat . 
Oct . 31, 1836. Killed a full grown female Kangaroo 
Rat. Eyes prominent, iris dark, pupil circular. It had 
in the pouch a young one without hair, the eyelids closed, 
pouch developed, nostrils open, lower lip formed, and 
mouth open in the centre and left side, tongue well 
formed, motions vigorous, and hanging on the teat; was 
removed at 5 r. m., and allowed to crawl upon the table. 
