From the Logbook of the White Star Liner Celtic

 

 

In the early 1900s, a ship’s logbook was divided into individual pages for each day of a voyage. A logbook page ran from midnight to midnight. At the top of the page, the name of the vessel, such as “RMS Titanic ,” would be written down along with the “From” and “To” ports of the current voyage (e.g., From Southampton , To New York), as well as the current day and date such as: “Sunday , 14th day of April , 1912.” Below this basic information at the top, the page was divided horizontally into two major parts, one for AM and one for the PM. Both AM and PM parts were each further subdivided horizontally into twelve one-hour segments, and data and remarks were listed in the appropriate hourly segment. In the middle of the page there was a printed section for recording noontime observations and other relevant pieces of information. Typically, in this middle section you would fined space for such things as:

 

-         Latitude and longitude at Noon by DR and by observation

-         Course and distance made good from last noontime position

-         Distance through the water by patent log

-         Currents in the 24 hours ending at noon

-         Compass variation

-         True bearing and distance to a given position at Noon

-         Coal consumed and coal remaining

 

The columns of the logbook were typically marked for:

 

-         Hour segment (1 through 12 in both AM and PM parts)

-         Distance run in nautical miles and tenths of a mile

-         Course by standard compass

-         Standard compass deviation

-         Patent log reading

-         Revolutions per minute (on each engine)

-         Wind: direction and force

-         Weather (sky conditions, etc.)

-         Sea state

-         Barometer and attached thermometer

-         Temperature: air, wet bulb, and sea

-         Remarks

 

Specific time notations of key events would be entered into the Remarks column as required along with a brief description of the event that took place at that time. The time given would be Bridge time, the time on the wheelhouse clock used by the watch-keeping crew. Typically, entries in the temperature, barometer, weather, sea state and patent log columns would be made every two hours in hour segments 2, 4, 6, 8 and 12 in each part. Entries for engine revolutions would be made every four hours in hour segments 4, 8 and 12 in each part. Course changes would be entered into the Remarks column. For example, in the lower PM part of Titanic’s scrap log page for April 14th there would have been an entry in the 6th hour segment that read something like, “5.50  42.00 N 47.00 W a/c N71W” where the course entered (N71W) would be by standard compass.

 

The following shows a logbook page that was used by the SS Celtic for 28 November 1914 when she was moored alongside the Keyham Wharf in Devonport while serving as an armed merchant cruiser:

 

From the logbook of the SS Celtic (http://www.naval-history.net/OWShips-WW1-08-HMS_Celtic.htm). 

 

Extracts from the logbook of the SS Celtic reveal how time changes were carried out in the early part of the 20th century, for both eastward as well as westward voyages. The following example is from the evening of December 25th and the morning of December 26th for her voyage from St. Vincent to Pernambuco in 1914:

 

PM segment from the Log of the SS Celtic 25 December 1914

 

AM segment from the Log of the SS Celtic 26 December 1914

 

From Noon of the 25th of December to Noon of the 26th of December, Celtic was heading south-westward, increasing her westward longitude. Notice that there is an entry in the 12th hour of the PM segment on the 25th of December that Clocks were put back 16 minutes. (In accordance with WSL practice, the adjusting of clocks took place close to Midnight each night so that at Local Apparent Noon [LAN] the next day the clocks would show 12:00.) The 16 minutes that were entered into the log was the total setback time. This amount of time also happens to agree with Celtic’s noontime positional data. On December 25th at Noon her observed longitude was 30° 03’ W. Her DR noontime longitude for December 26th was 33° 53’ W. The difference in GMT at LAN on the 25th and GMT at LAN on the 26th for those longitudes was exactly 15 minutes and 50 seconds, thus agreeing with the 16 minute setback that was made to the clocks on the night of December 25.

 

Also notice that on December 25th Celtic was advancing 12.7 nautical miles every hour carrying 62.0 revolutions per minute on her engines according to the data in the distance run column for the hourly segments in the PM that preceded the 12th hour. However, it ran 14.4 nautical miles in the 12th hour segment of the PM which ended at Midnight. Also notice that in the 1st hour of the AM segment for the December 26th the ship also ran 14.4 nautical miles. However, in the hourly segments for the AM that followed, her advance was back to 12.7 nautical miles. Throughout all this time, Celtic maintained 62.0 revolutions per minute on her engines and was on a course of S66°W by standard compass. (Magnetic variation at noon 25 December was 19° 30’ W. Compass deviation was put down as 1°W.)

 

It is obvious that the speed of the vessel was 12.7 knots while running at 62.0 revolutions per minute. But the reason for the greater advance in mileage for the last hour of December 25th and for the 1st hour of  December 26th is due to the way the total 16 minute clock adjustment time was carried out.  One-half of the total adjustment time, 8 minutes, was added into the 12th hour segment of the PM on December 25, and the other 8 minutes was added into the time of the 1st hour segment of the AM for December 26. This meant that those that served in the First Watch, from 8 p.m. to Midnight, served a total of 4 hour and 8 minutes on deck instead of their usual 4 hours, and those that served in the Middle Watch, from Midnight to 4 a.m., also served a total of 4 hour and 8 minutes on deck instead of their usual 4 hours.  We know this to be true by simply comparing  the ratio of 68 min/60 min = 1.13 to the ratio of the hourly run distances of 14.4/12.7 = 1.13. This proves that one-half of the full adjustment amount was applied in the last hour of December 25 and the other half in the first hour of December 26. Midnight, when 8 bells was struck, came at the end of the last hour of December 25.

 

The next example from the logbook of Celtic is taken from the evening of March 3rd and the morning of March 4th of 1915:

 

PM segment from the Log of the SS Celtic 03 March 1915

 

AM segment from the Log of the SS Celtic 04 March 1915

 

From Noon of the 3rd of March to Noon of the 4th of March, Celtic was heading north-eastward, decreasing her westward longitude. Notice that there is an entry in the 12th hour of the PM segment on the 3rd of March that Clocks were put forward 15 minutes. Again, the 15 minutes that were entered into the log was the total adjustment time. However, notice that Celtic was making 12.5 knots carrying 60.0 revolutions per minute on her engines at the time, and hourly distance run values all showed 12.5 nautical miles except for the 12th hour PM segment for the 3rd of March and the 1st hour AM segment for the 4th of March. These showed an advance of only 11.0 miles. If we take the ratio of hourly segment mileages we get 11.0/12.5 = 0.88 which happens to agree with the taking of the time ratios of 52.5/60 = 0.88. Putting the clock ahead takes time off an hourly interval.  One-half of 15 minutes is 7 ˝ minutes.  Thus we see that one-half the total adjustment amount was applied to the last hour of the 3rd of March and to the first hour of the 4th of March. This meant that those that served in the First Watch, from 8 p.m. to Midnight, served a total of about 3 hour and 52 or 53 minutes on deck instead of the usual 4 hours, and those that served in the Middle Watch, from Midnight to 4 a.m., served a total of about 3 hour and 53 or 52 minutes on deck instead of the usual 4 hours.

 

The examples from Celtic clearly show that clocks were adjusted close to midnight each night, either being “put forward” when the ship’s longitude was decreasing going eastward, or “put back” when the ship’s longitude was increasing going westward. We also see that one-half of the total adjustment amount was applied in the very last hour of one day, and the other half of the total adjustment amount was applied in the very first hour of the next day. For those in the First Watch, from 8 p.m. to Midnight, their time was extended or reduced in the very last hour of their Watch on deck. For those in the Middle Watch, from Midnight to 4 a.m., their time was extended or reduced in the very first hour of their Watch on deck.