Monday, 25 April 2011

Making water in the frozen seas

The Christmas berg, from p258 MCormick's Voyages of discovery

When reading Robert McCormick's (of HMS Erebus) account of Christmas in the frozen regions which Russell Potter posted here, my interest was piqued by the mention of the twelve tons of ice, "having just been taken on board, from a hummock, to complete our water".

National Archives, Crown copyright waived for non-commercial use

The logs of Erebus and Terror for Ross and Crozier's Antarctic voyage are held by the National Archives and, for a fee, copies can be downloaded from their website. The page for 23 Dec 1841, shown above, includes the following entries:
  • 1.40 shortened sail and made fast to a piece of ice. Employed watering.
  • 7.45 Cast off from the ice, made all plain sail
Which suggests that loading the 12 tons of ice took six hours.
The water reserves for that day are stated as 19.90 meaning 19 tons and 90 gallons.

The tedious task of transcribing the log entries for water into a spreadsheet resulted in some interesting results:

This chart shows the water reserves of HMS Erebus, the upper line in blue, and HMS Terror, the lower line in red.
The first thing to notice is the different capacity of the two ships. Terror's tanks could hold 6000 gallons or 26.8 tons, Erebus could carry 1000 gallons more for a total of 31 tons. From the 24 December the upper line slopes upward as the 12 tons of ice are melted and added to the tanks over a period of 7 days. The Terror's line shows two smaller and steeper upswings where ice was loaded, but in this case it was processed differently. Terror's log for 30 Dec 1841 includes the entries:
  • Short'd sail, lowered the topsails & secured the ship alongside a piece of ice.
  • Erebus fast to the same piece.
  • Emp'd filling tanks with ice.
Next to the figure for the water reserve is remarked "The additional quantity of water shown today is from the ice which was put in the tanks". This seems a wise move by Captain Crozier. He didn't encumber his decks with blocks of ice for a week and he didn't waste any fuel melting it.
Both ships dropped anchor in the Falkland Islands with around 12 tons in their tanks.

The horizontal parts of the chart would seem indicate times when, beset in the pack, the ships were melting ice for daily consumption.

Another interesting feature is the daily water usage for HMS Erebus.
While, in the latter part of the cruise, the Terror's water consumption was an unchanging 54 gallons per day the figures for Erebus Erebus show an interesting pattern of one day 85 gallons followed by two or three days at 66 gallons. What ever did they use those extra 19 gallons for ?

All in all this shows a few of the surprising results which can be teased out of old data by applying modern techniques. It is of particular interest if, like me, you share the view, originated by William Battersby, that the lead poisoning experienced on the fatal Franklin Expedition has its origins in the water making systems installed in these ships.