Mechanical and General Science. 365 
a very delicate apparatus, constructed on the principle of Coulomb, 
and capable of detecting the minutest traces of attraction, disco- 
vered very remarkable varieties of magnetic power in a time-keeper. 
By denoting the intensity of the terrestrial magnestism by 100, he 
found the intensity of the chronometer one inch above the centre of 
its crystal, to be respectively 90.79, 102.29, 90.69, and 78.89, ac- 
cording as XII was directed*north, east, south, and west. By deter- 
mining also the tntensity one inch below the bottom of the time- 
keeper, the intensities in the same directions were 77.17, 91.34, 
101.26, and 94.94. In like manner Mr. Harvey found, by deter- 
mining the intensities of the sides, that they were severally 105.61, 
89.61, 91.78, and 84.05. The intensity also one inch above the 
extremity of the steel arbour of the fusee was 109.09; and in the 
line of a common tangent, proceeding from between the barrel 
and fusee, XII being uppermost, 107.82. When, however, the 
chronometer was turned a quadrant, so as to bring the middle of the 
side of the spring-box an inch below the centre of the oscillating 
bar, IX being uppermost, the intensity amounted only to 92.223 
and over the small interval between the balance and. the fusee, 
it fellto 79.51. 
On examining the balance Mr. Harvey found the inner rims of 
the arcs of compensation to be of steel, and which, together with 
the time-screws, were in a state of active magnetism, particularly 
the latter, one having strong northern polarity, and the other 
southern. The small wormed cylinders also, on which the ther- 
mometer pieces moved, presented equal proofs of polarity, one 
being a north pole, and the other a south. When the north pole of 
a small bar magnet was placed near the extremity of the wormed 
cylinder which possessed northern polarity, the balance immediately 
receded a smal] quantity ; but when the south pole was applied, the 
power was sufficient to cause it to advance through a minute but 
sensible arc; and similar effects were produced when the proper 
poles of the magnet were presented to the extremity of the wormed 
cylinder having southern polarity. On presenting a more powerful 
magnet, the balance was drawn more than a quadrant from its 
quiescent position, and motion communicated to the chronometer. 
The effect of the balance on a pocket compass was observed in 
another experiment; and a table is given in the paper, illustrating 
the deviations produced in it, by moving the balance through given 
ares. An arc of 110° produced a deviation of 544°. A compass 
needle of a more delicate construction was inverted, the moment the 
time-screws had passed through an arc of 90°. A curious effect 
was also remarked by Mr. Harvey, by turning the balance through 
a greater arc than a quadrant, and thereby causing the north pole of 
the compass to point west, when, by allowing the balance to oscil- 
late, the compass needle ranged for many seconds through the com- 
Vou. XVII, ; 2C 
