Ba:ppickEr— On the Influence of Magnetism on the Rate of a Chronometer. 17 
These observations tend to increase considerably the interest in Barlow’s experi- 
ments, which, as mentioned before, are the only ones made with soft iron. 
Barlow had six excellent chronometers at his disposal (two pocket and four 
box chronometers), which he observed in the proximity of an iron ball of 18 ins. 
diameter, weighing 496 lbs. Preliminary experiments with a small compass-needle 
having been made in order to determine the magnetic intensity in the neighbour- 
hood of the ball, especially the zones of maximum and minimum intensity, the 
chronometers were put in different positions as to the iron ball, so as to vary the 
magnetic intensity, which was always previously ascertained by means of the 
above-mentioned small compass. This has only once been omitted (Tables IV. 
and V.), where the iron ball had been replaced by an iron plate, such as Barlow 
proposed elsewhere, for the compensation of the deviation of a compass [cef. p. 44]. 
His experiments are given extensively in six Tables, of which the following Tables 
form an abstract. The temperatures were read daily at 10 o’clock, a.m. The 
values I give are the means of the daily figures in Barlow’s Tables. The other 
columns do not require further explanation: it is only to be added, that Barlow 
gives the results chronologically, while I arranged them according to the magnetic 
intensities, with the exception of Table II. The figures in the first column show 
how the experiments followed each other in time. 
Taste I.—Pocket Chronometer (Earnsuaw), assumed Detached Rate — 3°:2 losing. 
Chronol. | No. of Days. | Temperature.| Intensity. | Position Rate. neta Remarks. 
Ne: ea Detached Rate. | 
3 6 47 91 5. — 5°6 — 255 S. of ball. 
1 12 = [100] = ~ 3-2 sas oa 
2 4 49 100 — - 3:2 — — 
As the rate was very irregular, when the chronometer was again detached, 
the observations were discontinued after the above experiments were made. 
TRANS. ROY. DUB. SOC., N.S. 
VOL. It. 
[Tasue II. 
