• Home
  • Brief History
  • The Greenwich Meridian
  •  
  • Greenwich (1675–1958)
  • Herstmonceux (1948–1990)
  • Cambridge (1990–1998)
  • Outstations (1822–1971)…
    • – Chingford (1822–1924)
    • – Deal (1864–1927)
    • – Abinger (1923–1957)
    • – Bristol & Bradford on Avon    (1939–1948)
    • – Bath (1939–1949)
    • – Hartland (1955–1967)
    • – Cape of Good Hope    (1959–1971)
  •  
  • Administration…
    • – Funding
    • – Governance
    • – Inventories
    • – Pay
    • – Regulations
    • – Royal Warrants
  •  
  • Contemporary Accounts
  • People
  • Publications
  • Science
  • Technology
  • Telescopes
  • Chronometers
  • Clocks & Time
  • Board of Longitude
  •  
  • Libraries & Archives
  • Visit
  •  
  • Search

Statistics relating to the chronometer trials (1822–1915)

 

page under construction

On the the 26 June 1821, the London Gazette (p.1351) carried the following announcement:

'The Lords Commissioners of the Admiralty being desirous of increasing the number of chronometers for the use of His Majesty's Navy, and of encouraging, the improved manufacture of that important article,  do hereby give notice, that a depôt for the reception of chronometers is opened at the Royal Observatory of Greenwich, where the makers will be permitted to deposit their chronometers in order to their being tried, and ultimately, if they should be found worthy of selection, purchased for the use of the Navy, or of being disposed of by the proprietors to private purchasers.

And for further encouragement, their Lordships will purchase at the end of each year, the chronometer, which, shall have kept the best time, at the price of £300, and the second best, at the price of £200, provided that there have been above ten chronometers in the competition, and that the said best chronometers shall keep their rates within certain limits to be hereafter stated; the other chronometers their Lordships may purchase as they may think proper, at such sums as may be agreed upon with the makers. And their Lordships have reason to expect, that their annual rate of purchase for some years to come will be not less than ten chronometers in each year.

Every facility will be afforded to the makers who may place their chronometers in the depôt, for disposing of any of them to private purchasers; and every information will be afforded to purchasers as to the rates of going of the chronometers, of which a strict account will be kept under the direction of the Astronomer Royal and Board of Longitude.

The further conditions and regulations connected with this arrangement may be learned of the Astronomer Royal at Greenwich, or of the Hydrographer of this Office. J. W. Croker.'

From 1828 instead of agreeing to purchase the two best chronometers, the Admiralty instead purchased the best three for £200, £170, and £130 respectively, the decison being announced in the 25 July edition of the London Gazette:

'His Royal Highness the Lord High Admiral, referring to the advertisement from this Office, dated the 25th June 1821, hereby gives notice, that, until further directions, it is His Royal Highness's intention to purchase three prize chronometers, instead of two, at the following rates, viz.

For the best, - £200
For the second best, - £170
For the third, - £130

Subject to the conditions set forth in the said advertisement, and to certain limits of rates, which may be known on application to the Astronomer Royal at Greenwich. J.W. Croker.'

The first trial began in February 1822, and was followed by twelve others. Each of the trials, which became known as the ‘Premium Trials’, lasted for a period of 12 months. They were discontinued in 1836 as no useful purpose seemed likely to be served by continuing them. Over the course of the trials, there had been no marked improvements nor had there been any new inventions or discoveries. Worse still, some individuals had abused the system by entering chronometers that they had not made.

The trials of chronometers for purchase by the Board of Admiralty commenced a few years later in 1840. What is striking, is that there appears to have been no standardised format for these later trials until 1879, when Airy was nearing retirement. What is also striking is how cold the chronometer room often was during the winter months, with sub zero centigrade temperatures being recorded in most of the trials that took place prior to 1869.

Apart from the tables relating to the Premium Trials, all the tables below have been compiled from information published in the volumes of Greenwich Observations. They cover the period from 1840 to 1915 when the trials were discontinued.

The following pages may also be of interest.

The Chronometer Rooms at Greenwich

Rates of chronometers and watches on trial at the Observatory, 1766–1915

 

The order of merit – the 'trial numbers'

When the Premium Trials started, It would appear that the manner of deciding the order of merit of those that had been entered was still undecided (RGO14/23/6o(b)-68). At the end of the first trial, following a discussion by a committee of the Board of Longitude (Pond, Wollaston, Kater, Colby. Herschel & Young), it was decided to calculate a 'trial number', the premiums being awarded to the chronometers with the lowest trial number. The trial number was calculated:

'by taking the difference of the greater and lesser mean monthly rate, and multiplying the same by 2, and adding thereto the mean of the monthly extreme variations.'

Despite the fact that when the trials were announced it was stated that the successful 'chronometers shall keep their rates within certain limits to be hereafter stated, no limits appear to have been applied to the first trial.

From the second trial onwards, it was decided that the various awards would not be given to the best performing chronometers unless their trial numbers were also below certain limits, the announcement seemingly being made only about a week before the trial started. The limits changed over time and were applied as follows:

Ist trial
No limits appear to have been applied

2nd trial onwards
First premium, not exceeding 6s, second premium, not exceeding 10s (announcement first made in the 2 May edition of The Edinburgh Gazette and the 3 May 1823 edition of the London Gazette)

7th trial onwards
First premium, not exceeding 5s, second premium, not exceeding 6s, third premium, not exceeding 7.5s

10th trial onwards
First premium, not exceeding 3.5s, second premium, not exceeding 4.5s, third premium, not exceeding 6s

11th trial onwards
First premium, not exceeding 2.5s, second premium, not exceeding 3.5s, third premium, not exceeding 4.5s

When the trials of chronometers for purchase by the Board of Admiralty started in 1840, the method of calculating the trial number was altered, the following equation used instead:

trial number = a + 2b

in which (a) represents the algebraic difference between the greatest and least weekly rates during the trial, expressed in seconds and (b) the greatest algebraic difference between two consecutive weekly rates

Interestingly, although the results of the trials from 1840 onwards were published in Greenwich Observations, the trial numbers were alwasy omitted even though they had been calculated. Instead, the results were simply listed in order of merit.

Not only was there no mention of trial numbers in the published results, there was no mention of them in the  Reports of the Astronomer Royal either until 1887, when the following account was given of how trial numbers were calculated for the recently commenced series of trials of Deck watches:

'In order to compare the performances of the several watches, "trial numbers," representing deviations in weekly rates, have been formed on the same general principles as for the chronometer trials. The trials in different positions introduce, however, a new element, and an arbitrary weight must be assigned to them in combining them with the trials "dial up." It has been considered that when the watch is worn in the pocket the pendant will generally be "up," and that not more than one-third of the deviation" pendant right" or "pendant left" is likely to have practical effect.

Putting

           a = Difference between greatest and least weekly rates "dial up,"
           b = Greatest difference betweeb one week and the next "dial up,"
           c = Difference between weekly rates "pendant up" and "dial up,"
           d = Difference between weekly rates "pendant right" and "dial up,"
           e = Difference between weekly rates "pendant left" and "dial up,"

the quantity c + d/3 + e/3 may be taken as the measure of deviation in weekly rate due to positions in ordinary wear. Half weight has been given to this quantity in combining it with the trial number "dial up" (a +2b), on the assumption that the deck-watch would be usually lying "dial up" and that it would not be carried in the pocket more than eight hours a day on average.. Thus the quantity a +2b +1/2(c +d/3 +e/3). has been adopted as the trial number for deck-watches.'

 

Statistics relating to the Premium Trials (1822–1836)

It has not been possible to locate complete sets of the published data for all thirteen trials. A bound volume (ref: 10/5/995) held at the National Maritime Museum contains complete sets of data for six of the trials (2nd, 6th, 8th, 11th, 12th, & 13th) and partial data for the remainder. The Cambridge digital library has a set for the 1st (RGO14/23/32). Missing data has been taken from other sources as indicated by the footnotes.

Trial  
Dates

Weeks 
No. on trial
at start
No. on trial
at end
Min & Max
midday
Temp. oF
1st
1822 Feb
 to 
1823 Jan
52
 31 a
 16 b
 25 & 80
 2nd 1823 Mar 1824 Feb 52 36 c 18 34 & 71 f
3rd 1824 Apr 1825 Mar 52 31 e d 7 36 & 70 g
4th 1825 May 1826 Apr 52 48 e 10
 25 & 82 g
5th 1826 Jun 1827 May 52 59 18 e 29 & 79
6th 1827 Jul 1828 Jun 52 58 25 35 & 78 g
7th 1828 Aug 1829 Jul 52 79 e 26
 29 & 73 g
8th 1829 Sep
 1830 Aug
 52 57 22
 29 & 80
9th 1830 Oct 1831 Sep 52 73 e 28
 27 & 78 g
10th 1831 Nov 1832 Oct 52 63? e h
 23 39 & 78 g
11th 1832 Dec 1833 Nov 52 57 10 37 & 77 g
12th 1834 Jan 1834 Dec 52 28 7 40 & 81 g
13th 1835 Mar 1836 Feb 52 56 1 27.5 & 82
Footnotes:

a) Of these, 14 were taken to Madeira between 12 Jul & 4 Sep 1822
b) Of these, 10 were taken to Madeira between 12 Jul & 4 Sep 1822
c) Of these 16 were sent to Falmouth for survey work from 25 July to 24 September
d) During this trial, at least 23 chronometers were sent to the Baltic, returning on 13 September
e) Figures from the Nautical Magazine (1833) and The Nautical Magazine (1832). These figures
    should not be relied on as some of the published figures are known to be incorrect
f)  The cover sheet of the published results for the thirteenth trial incorrectly records the figures as 34 & 70
g) From the cover sheet of the published results for the thirteenth trial
h) The two olumes of the Nautical Magazine mentioned in e) give different figures (62 & 63)

 

Chronometers awarded the premium prizes and their trial numbers (1823–1836)

Trial  
Ending Year
of trial
Prize
Chronometer
Trial
Number (s)
1st 1823 1st Barraud 957 11.29
  2nd Pennington 154 12.87
 2nd 1824 1st Murray 816 4.44
2nd Cathro 1512 6.84
3rd 1825 1st Widenham 929 5.44
2nd French 1640 6.12
4th 1826 1st French 20/3912 2.62
2nd French 957 3.46
5th 1827 1st McCabe & Strachan 167 4.68
2nd Young 78 3.65
6th 1828 1st Guy 1410 4.41
2nd Young 85 4.52
7th
 1829 1st Dent 114 2.27
2nd Carter 131 3.80
3rd Molyneux 943 4.00
8th 1830 1st Baker 865 3.59
2nd Carter 137 4.04
3rd Murray 640
 4.34
9th 1831 1st Cotterell 311 2.93
2nd Frodsham 2 3.65
3rd Webster 665 3.73
10th 1832 1st Molyneux 1038 2.82
2nd Young 110 2.95
3rd Webster 675 3.09
11th 1833 1st       not awarded n/a
2nd Appleton 145 3.15
3rd Molyneux 1263 3.68
12th 1834 1st       not awarded n/a
2nd       not awarded n/a
3rd Carter 144 4.27
13th 1836 1st       not awarded n/a
2nd       not awarded n/a
3rd Carter 160
 4.53b ref
Footnotes:

a) Barraud 957 & Pennington 154 were both amongst the chronometers sent to Madeira during the trial
b) Awarded even though the performance exceed the trial limits 'due to the severity of the weather'

 

The Admiralty Trials from 1840 to 1850

These trials all took place in the same room as the Premium Trials. It was located on the first floor towards the eastern end of the Meridian Building. The room was unheated except where noted in the column headed Test sequence. In each of these years, not all the chronometers were present at the start of the trial.

Explanation of column headings:
  • Weeks = duration of trial in weeks
  • Test sequence = the number of weeks under different conditions
    • unbracketed = number of weeks when the room was unheated
    • { } = number of weeks when the room was heated by a stove
    • [ ] = number of weeks when (all) the chronometers were 'exposed to the open air at a North window' (1849 & 1850 only). This was done by placing them near an open window
    • ( ) = number of weeks when (all) the chronometers were 'placed in a tray above the stove' (1849 & 1850 only)
  • Min Temp = coldest temperature recorded inside the room during the trial
  • No. on trial = number of chronometers mentioned in the published reports. Also believed to be the number submitted for trial
  • H+C = Number of chronometers in the trial which at various times were 'exposed to the open air' at a penthouse at a window on the south side of the room (S) or a penthouse at a north window elsewhere in the building (N), These chronometers were also exposed to heat. In 1841 & 1842 this was done be placing them in a closet (presumably elsewhere in the building) and in the years 1843-1848 by placing them near the stove at a temperature of about 100oF
 
Dates

Weeks 
Test sequence
Min Temp. oF
No. on trial 
H+C
test

1840 Jan 11
 to 
Aug 15  
 31
 31
 32
 28
 2 (S, Clt)
1841 Jan 9 Sep 4 34 34 25 29 2 (N, Clt)
1842 Jan 8a
 Jul 16
 27 8 {4} 11 {4}
 31 40 2 (N)
1843 Jan 14b
 Jul 15 26 14 {3} 4 {3} 2 30 29 3 (N)
1844 Jan 13 Jul 13 26 6 {3} 12 {3} 2 31 35 9 (N)
1845 Jan 18
 Jul 12
 25 4 {1} 1 {1} 2 {2} 7 {1} 4 {2}
 29 34 5 (N)
1846 Jan 17
 Jul 4
 24 11 {3} 6 {2} 2
 34 48 6 (N)
1847 Jan 16 Jul 10 25 12 {2} 7 {3} 1
 29 56 7 (N)
1848 Jan 15
 Jul 8
 25 10 {4} 7 {2} 2
 28 48 10 (N)
1849 Jan 13
 Jun 23
 23 [6] (1) {1} 3 {1} (1) 5 {1} (1) 3
 n/ac
 31 n/a
1850 Jan 12
 Jul  6
 25 [4] (2) 2 {1} [2] 10 (2) 2
 25d 26 n/a
Footnotes:

a: One chronometer started the trial six weeks earlier on 27 Nov 1841
b: Trial officially started 1842, Dec 10, but no results recorded until week starting 14 Jan
c. Not recorded
d: This is when the window was open and all the chronometers were 'exposed to the open air at a North window'

Trials in the second Chronometer Room (1851–1868)

During these years, all the trials had a period where the chronometers were exposed during the winter months for a number of weeks in the open air. They were also subjected to a number of weeks exposure to gentle heat in an early form of chronometer oven.

Explanation of column headings:
  • Weeks = duration of trial in weeks
  • Test sequence = the number of weeks under different conditions
    • unbracketed = number of weeks when the room was unheated
    • [ ] = number of weeks when all the chronometers were 'exposed to the open air
    • ( ) = number of weeks when all the chronometers were exposed to artificial heat
  • Min Temp = coldest temperature recorded inside the room during the trial
  • No. submitted = number of chronometers sent in for trial
  • No. in first week = number of chronometers present in first week of trial
 
Dates

Weeks 
Test sequence
Min.
temp
oF
No. in
Report  
No. Sub-
mitted
No. in
1st week

1851 Jan 11
 to 
July 5  
 25
 [9] (4) 8 (2) 2
 28
 20
 ?
 5
1852 Jan 10 Jul 3 25 1 [3] (2) [4] 5 (3) 7 21
 17 17 1
1853 Jan 8 Jul 9 26 [7] (4) 9 (3) 3 22
 19 19
 10
1854 Jan 7 Jul 8 26 [4] (4) 8 (3) 7 29
 14 2
1855 Jan 6 Jul 7 26 [4] 5 (3m) 5 (3h) 6 17
 20 20 1
1856 Jan 12 Aug 9 30 [4] 1 [1a] (3m) 9 (3h) 9   24
 20 20 7
1857 Jan 3 Aug 8 31 [71] 4 (4) 9 (3) 4 21
 22 22 2d
1858 Jan 9 Aug 7 30 [4] 6 (4) 7 (4) 5 23
 36 36 15
1859 Jan 8
 Jul 30
 29 [5] 1 (3) 11 (4) 5
 30
 34 37 23
1860 Jan 7
 Jul 28
 29 [13a] (3) 7 (3) 3
 25
 51 52 21
1861 Jan 5
 Aug 3
 30 [6] 2 (3) 11 (4) 4
 24
 58 61 30
1862 Jan 11 Jul 19 27 [2] 2 [4c] (3) 6 (4) 6
[2] 2 [4c] 3 (3) 7 (4) 2
 21

 36 +
36
72 72
1863 Jan 10
 Jul 18
 27 [6b] (3) 10 (4) 4
 38
 57 59 59
1864 Jan 9 Jul 23 28 [8b] 2 (4) 6 (4) 4 31
 57 57 57
1865 Jan 7
 Jul 29
 29 1 [7b] 1 (4) 9 (4) 3
 32
 46 46 46
1866 Jan 13 Aug 4 29 4 [4b] 1 (4) 6 (4) 6 31
 56 59 59
1867 Jan 12 Aug 3 29 [4b] 3 (4) 10 (4) 4 30
 55 57 57
1868 Jan 11 Jul 18 27 [5b] 3 (4) 8 (4) 3 36
 44 45 45
Footnotes

a)  Except for last two days
b)  At open window rather than in pent-house
c)  Except for last two days, At open window rather than in pent-house
d)  Ten in second week
h)  High temperature
m) Moderate temperature

Trials in the Upper Chronometer Room (1869-1887)

From 1869 onwards, the trials were conducted in a newly fitted out Chronometer Room underneath the Great Equatorial Telescope. Although the north west window of the room was fitted with a railed outhouse so that the chronometers could be tested in the 'open air', it was never used in any of the trials. As can be seen from the table below, the temperature in the room never normally dropped below freezing (32oF), the two exceptions being the years 1880 and 1881. Of these, 1880 was the coldest, with the internal temperature dropping to 24oF in the week Jan 24-31. Elsewhere, Airy also records that on Jan 27, the outside temperature dropped to 17.2oF. He also records that the average outside temperature for the period Jan 12-26 1881, was only 24.2oF which was 14.7oF below average and that the temperature fell below 20oF on 10 days and rose above freezing point on only three days, the highest temperature during the period being 35.3oF and the lowest 12.7oF.

The chronometer room was fitted with a newly constructed oven which was modified in 1885. In his 1885 Report, Christie was to tell the Visitors that:

'As much difficulty is experienced in maintaining the chronometer oven at a nearly constant temperature, an apparatus has been procured from Mr. Kullberg which is designed to effect this automatically, by the action of a compensation-bar, which, as the temperature rises, gradually closes a small hole through which the supply of gas to the gas burners passes. The apparatus has not yet been brought into use, as the chronometer oven has been constantly required for testing chronometers since it has been received.'

It was eventually brought into use in November in time for the 1886 trial.

Explanation of column headings:
  • Weeks = duration of trial in weeks
  • Test sequence = the number of weeks under different conditions
    • unbracketed = number of weeks when the room was unheated
    • ( ) = number of weeks when all the chronometers were exposed to artificial heat
  • Min Temp = coldest temperature recorded inside the room during the trial
  • No. in Report = number of chronometers for which details were published
  • No. submitted = total number of chronometers sent in for trial
 
Dates

Weeks 
Test sequence
Min temp  
oF
No. in
Report  
No.
Submitted

1869 Jan 9
 to 
Jul 31  
29
 8 (4) 9 (4) 4
 39
 46
 ?
1870 Jan 15 Aug 6 29 10 (4) 5 (4) 6 33 36 39
1871 Jan 14
 Aug 5
 29 7 (4) 9 (4) 5
 36 44 44
1872 Jan 13
 Aug 3
 29 8 (4) 9 (4) 4
 44 40 40
1873 Jan 11
 Aug 9
 30 8 (4) 7 (4) 7
 35 41 41
1874 Jan 10
 Aug 8
 30 8 (4) 10 (4) 4
 36 40 40
1875 Jan 9
 Jul 31
 29 10 (3) 9 (4) 3
 40 49 49
1876 Jan 15
 Aug 5
 29 7 (4) 10 (4) 4
 37 47 47
1877 Feb 10
 Sep 1
 29 6 (4) 9 (4) 6
 40 35 35
1878 Jan 12
 Jul 27
 28 6 (4) 8 (4) 6
 40 29 29
1879 Jan 11
 Jul 26
 28 7 (4) 7 (4) 6 35 30 30
1880 Jan 10
 Jul 24
 28 7 (4) 7 (4) 6 24 44 44
1881 Jan 15
 Jul 30
 28 7 (4) 7 (4) 6 31 43 43
1882 Jan 14
 Jul 29
 28 7 (4) 7 (4) 6
 45 46 46
1883 Jan 13
 Jul 28
 28 7 (4) 7 (4) 6 42
 40 40
1884 Jan 12
 Jul 26
 28 7 (4) 7 (4) 6 44 34 34
1885 Jan 10
 Jul 25
 28 7 (4) 7 (4) 6 41 45 45
1886 Jan 9
 Jul 24
 28 7 (4) 7 (4) 6
 42 37 37

 

Trials in the Upper Chronometer Room (1887-1915)

In his Annual Report for 1886, Christie told the Visitors that:

'As the termination of the annual trial falls at an inconvenient part of the financial year for the purchase of chronometers, it has been decided to make the trial commence in future on the first Saturday in July, so that it would end in the latter part of January. The temperature conditions in the room will be practically the same as at present, but in reverse order, commencing with warm weather and ending with cold. The rating is to be for 29 weeks, viz., three periods of 7 weeks each in the room and two periods of 4 weeks each in the oven.'

However, as it was also desired to increase the stock of Navy chronometers without delay, a supplementary trial was commenced on March 5 and terminated on  June 18, just before the commencement of the 'ordinary' annual trial.

A second chronometer oven was installed in front of the north-west window in 1896. It is thought to have been (about?) the same size as the existing one.

'1888/9 trial the chronometers have been tested in the oven at temperatures of 80° and 85°, as well as at temperatures of 95° and 97° Fahrenheit, so that any residual secondary error of compensation would be made evident in the range of temperature from 42° to 98°.'

Explanation of column headings:
  • Weeks = duration of trial in weeks
  • Test sequence = the number of weeks under different conditions
    • unbracketed = number of weeks when the room was unheated
    • ( ) = number of weeks when all the chronometers were exposed to artificial heat
  • Min Temp = coldest temperature recorded inside the room during the trial
  • No. in Report = number of chronometers for which details were published
  • No. submitted = total number of chronometers sent in for trial
 
Dates
Weeks 
Test sequence
Min temp  
oF
No. in
Report  
No.
Submitted
1887 Mar 5 to  1887 Jun 18 15 a 3 (3) 3 (3) 3 39.0 52 52
1887 Jul 2  
1888 Jan 21      29 7 (4) 7 (4) 7 37.6 28 ?28
1888 Jul 7
1889 Jan 26 29 7 (4) 7 (4) 7 41.6 47 47
1889 Jul 6
1890 Jan 25 29 7 (4) 7 (4) 7 42.4 46 ?46
1890 Jul 5
1891 Jan 24 29 7 (4) 7 (4) 7 34.2 38 ?38
1891 Jul 4
1892 Jan 23
 29 7 (4) 7 (4) 7 40.8 51 51
1892 Jul 2
1893 Jan 21
 29 7 (4) 7 (4) 7 36.9 48 48
1893 Jul 1
1894 Jan 29
 29 7 (4) 7 (4) 7 34.9 43 43
1894 Jul 7
1895 Jan 26
 29 7 (4) 7 (4) 7 40.5 60 72
1895 Jul 6
1896 Jan 25
 29 7 (4) 7 (4) 7 42.1 63 b 83
1896 Jul 4
1897 Jan 23
 29 7 (4) 7 (4) 7 41.5 66 b
 97
1897 Jul 3
1898 Jan 22
 29 7 (4) 7 (4) 7 40.7 78 b
 98
1898 Jul 2
1899 Jan 21
 29 7 (4) 7 (4) 7 46.0 74 b
 103
1899 Jul 1
1900 Jan 20
 29 7 (4) 7 (4) 7 42.6 62 b
 85
1900 Jul 7
1901 Jan 26
 29 7 (4) 7 (4) 7 38.7 56 b 76
1901 Jul 6
1902 Jan 25
 29 7 (4) 7 (4) 7 44.5 51 b 70c
1902 Jul 5
1903 Jan 24
 29 7 (4) 7 (4) 7 43.4 31 b 47
1903 Jul 4
1904 Jan 23
 29 7 (4) 7 (4) 7 d
 43.1 40 b 68 e
1904 Jun 18
1905 Jan 7
 29 7 (4) 7 (4) 7 41.2 43 b 67
1905 Jun 17
1906 Jan 6
 29 7 (4) 7 (4) 7 44.2 26 b 59
1906 Jun 16
1907 Jan 5
 29 7 (4) 7 (4) 7 42.0 25 b 46
1907 Jun 15
1908 Jan 4
 29 7 (4) 7 (4) 7 45.0 15 b 28
1908 Jun 20
1909 Jan 9
 29 7 (4) 7 (4) 7 41.2 33 b 48
1909 Jun 19
1910 Jan 8 29 7 (4) 7 (4) 7 45.8 42 b 66
1910 Jun 18
1911 Jan 7 29 7 (4) 7 (4) 7 47.3 34 b 62
1911 Jun 17
1912 Jan 6 29 7 (4) 7 (4) 7 49.0 39 b 55
1912 Jun 15
1913 Jan 4 29 7 (4) 7 (4) 7 48.8 35 b 53
1913 Jun 21
1914 Jan 10 29 7 (4) 7 (4) 7 50.0 23 b 53
1914 Jun 20
1915 Jan 9 29 7 (4) 7 (4) 7 48.8 24 b 42
Footnotes:

a) Supplementary trial
b) excludes those that were rejected because the difference in rate between one week and
    the next exceeded 12 seconds
c) AR's report says 18 were rejected. The table of results lists 51 rather than 52 chronometers
d) The results table records 7 (4) 5 (1) 1 (3) 7, but an examination of the temperatures
    indicates that if followed the normal pattern of 7 (4) 7 (4) 7
e) AR's report says 26 were rejected and 42 were not. The table of results lists 40 rather than
    42 chronometers