Lovering and Bond on Magnetic Observations at Cambridge. 33 
which we were engaged; but the Thermometer has been ob- 
served regularly since the first trial every 20 minutes whenever 
magnetic observations are made. The magnetic observations were 
conducted on all these days with the same strictness as on the 
Term-days at intervals such as have been denoted; 12 or 13 
readings determining the place of the magnetic meridian for every 
required period. There may be times during every time of ob- 
servation when the arc of vibration is too large to allow of this 
process and then the 12 readings are suspended and the extreme 
limit of every oscillation is recorded. The expense of the Plates 
has precluded the idea of publishing all the diurnal curves which 
have been thus obtained. A specimen has been selected which will 
give an impartial view of the whole investigation. On Plate VI. 
the thermometric curves corresponding to the five October days 
may be studied by attending to the directions given on the face of 
it. The remarkable points are arranged in the following Table. 
Abstract of the October Thermometric Curves. 
Date. Time of Mini- Time of Maxi- Daily range of 
mum Heat. Thermometer. mum Heat. ‘Thermometer. 
Civil Time. |Cambridge M. T. Cambridge M. T. Thermometer. 
Oct.21 |6"10’ A.M 50° 20’ | 1" P.M) 54° 3° 40! 
Gr 795 |W cs 46 2 ge 51 30' 5 30 
(lu DBr Bir Ot «66 34 Q ue 62 28 
“94 16 50 “€ 40 40 |2 40'« 53 12 20 
OES NT eneyo) 37 \11 A.M.| 47 20 10 20 
Means. By oe ee 41 36 1 20P.M.| 53 34 11 58 
Meancurve|6 10 “ 43 Q oe 52 15 9 15 
The absolute changes of temperature from day to day cause the 
difference between the means of the numbers attached to the five 
days and the mean curve, as in the two last lines of the Table. The 
mean curve is drawn by adding together the figures observed at 
5 
