TOTAL SOLAE ECLIPSE OF JULY 18, 1860. 
343 
The average daily rate of this chronometer was therefore gaining 0*91 sec. ; and 
assuming this rate to have continued, on July 5 0^ its error would have been fast of 
Greenwich mean solar time 6‘3 seconds. 
On the supposition that the pocket chronometer would continue to lose 1’71 sec. daily, 
and that the box mean- time chronometer would continue to gain daily O' 91 sec. 
box chronometer Frodsham 3094 would gain over Frodsham 9768 . . 2'62 secs, daily. 
The subjoined Table contains the assumed errors of each chronometer, the estimated 
difference between the two chronometers, and the difference actually observed as nearly 
as possible at noon of each day — the observation being reduced to noon : — 
. 
Date. 
Assumed error of 
Frodsham 3094. 
Assumed error of 
Frodsham 9768. 
Estimated difference 
between 9768 and 3094. 
Observed difference 
between 9768 and 3094. 
sec. 
sec. 
sec. 
see. 
July 5. 
fast 6‘3 
slow 17'3 
-23*6 
-24*5 
July 6. 
fast 7'2 
slow 19'0 
— 26*2 
July 7. 
fast 8*1 
slow 20*7 
— 28*8 
July 8. 
fast 9‘0 
slow 22*4 
— 31*4 
July 9. 
fast 9-9 
slow 24*1 
-34*0 
-35*0 
July 10. 
fast 10-8 
slow 25*8 
-36*6 
-37*0 
j July 11. 
fast 11-7 
slow 27*5 
-39*2 
-37*5 
July 12. 
fast 12-6 
slow 29'2 
— 41*8 
-37*5 
1 July 13. 
fast 13*6 
slow 30*9 
-44*5 
-38*5 
1 July 14. 
fast 14*5 
slow 32*6 
-47*1 
-40*0 
July 15. 
fast 13’4 
slow 34*3 
-49*7 
— 41*5 
1 July l6. 
fast l6"3 
slow 36*1 
-52*4 
-42*5 
On examining the two box chronometers immediately after our arrival at Fivabellosa, 
Leplastrier 2915 was found to be apparently uninjured, but I was chagrined to find that 
Frodsham No. 3094 had been most severely disturbed by the joltings of our vehicle, 
notwithstanding the protection of its outside padded case, and an extra precaution I had 
taken to press shavings into its own case, to keep it firm in its place. The cap of the 
glass had become unscrewed, the glass had shaken out, and the chronometer itself, shift- 
ing from its normal position, had risen out of its seat ; fortunately, however, the glass 
could not move far, on account of the wadding, and the hands were consequently un- 
injured. I succeeded in replacing the chronometer, and in putting the glass into its 
frame ; but it thenceforward took up an entirely new rate, as was evident on comparing 
the differences between its readings and those of the pocket chronometer. An inspec- 
tion of the foregoing Table shows that up to the 10th the two chronometers maintained 
the average rate assigned to each; for example, the computed difference minus the 
observed difference on that day amounted to only — 0'4 second. After my return to 
England, chronometer No. 3094 was, with the Astronomer Royal’s kind permission, again 
compared by Mr. Ellis, who found the following errors from Greenwich mean time : — 
3 A 2 
