“Of Ships and Men: What can modern forensics tell us about their fate?”
Lead has some surprising properties, it is resistant to strong acids like Sulphuric acid, but is attacked by weak acids such as may be found in fruit juice. There have been documented cases of people getting lead poisoning from fruit juice served in lead-glazed ceramic jugs brought home as souvenirs.
Distillation has also been a culprit. As water condenses from vapour it absorbs carbon dioxide from the air to make carbonic acid. This weak acid has been implicated in poisoning cases where lead-soldered radiators were employed as condensers in illicit moonshine stills, and in crudely constructed rum distilleries in the eighteenth century West Indies.
Canned tomatoes have been also been a cause of lead poisoning, the fruit's acid leaching lead from the soldered seams of the cans. This principle has famously been proposed as the source of the lead exposure on the Franklin expedition, but faces the obstacle that the only canned provisions which appear in the expedition's victualling manifests are of low-acidity. There are canned meats and soups, but no canned fruit or other acidic canned products are listed.
I feel considerable sympathy for Stephan Goldner, the supplier of the canned food, or "preserved provisions" as it was called in the day. Goldner is reported to have had a prickly personality but his downfall was caused by a change to the production process, requested by the Admiralty, some time after the Franklin expedition had sailed. Nonetheless, from the early 1850s, when the scandal of the putrid meat in the Naval storehouses erupted, Goldner was villified for decades. He was called a miscreant and a traitor, one old Arctic hand even wrote that he should have been hanged - twice.
That abuse is not connected in any way to the lead from cans theory, which is a valid scientific hypothesis, albeit one which I have argued against.
|Original artwork by Kristina Gehrmann|
However, several of William's interpretations of the evidence proved questionable and were later reinterpreted in our co-authored paper, for the Newcomen Society, on the equipment of the ships. Perhaps most significant is the fact that a simple comparison of physical constants (latent heat of fusion = 334 joules per gram, latent heat of vaporisation = 2,230 joules per gram) suggests that for a given quantity of heat energy you get more than six times more water by melting ice than you get by boiling water for distillation. In other words, making drinking water by distillation of sea water is an insane waste of energy if there is ice or snow available to melt.
City of London Medical Officer Dr. Henry Letheby, stated in evidence to a Parliamentary Committee:
... of all adulterations of that kind, introduction of poisonous pigments into confectionery is the most common and the most serious, There is not an article of confectionery in this country which is not so coloured, I have before me a sample of such confectionery, in which there is enough chromate of lead to do serious mischief,...Coloured candy of the era was truly the "mutual friend" of doctors and gravediggers.
I promised every member of the audience a lick but no one took me up on the offer ☹️
|My local sweetshop|
What about the spongy bone! I hear you cry. Anne Keenleyside's marvelous analysis of the bones found on King William Island shows a high ratio of lead levels between the spongy (trabecular or cancellous) bone and the dense (cortical) bone. Spongy bone has a large surface in contact with the blood, so its lead content is indicative of blood lead levels. Lead incorporated in the mineral structure of dense bone is locked away out of reach of the blood. Comparison with the same ratio for workers exposed to atmospheric lead pollution, led to the conclusion that the lead exposure was relatively recent.
However, there are circumstances in which lead locked away in the dense bone is released into the blood stream. One well known example is pregnancy, which must be considered unlikely in this case. A better example can be found in cases of treatment of obesity by gastric banding. In such cases the body seems to exhibit a starvation reflex and starts mining the bones. In the case of Franklin's men the comparison is obvious, lead which had been laid down in the dense bone many years before was released into their blood stream while they were starving to death.
There are other cases where comparisons with healthy modern people subject to atmospheric pollution are not helpful. After all, there was no lead smelter or automobile battery factory in the vicinity of the ships.
But what about the lead in the hair! Surely that proves they were ingesting lead during the expedition?
Well, no. Firstly the lead levels in the hair are extraordinarily high. In the case of John Torrington about twenty times the level of a man who was deliberately poisoned to death, with lead, by a love rival. Clearly, Torrington did not ingest twenty times the lethal dose of lead week after week in the months before his death with no signs of lead poisoning. The vast majority of the lead in the hair must therefore be from an external source and not from his diet.
This another case where comparison with atmospheric pollution is not helpful. When hair is contaminated with lead particles from the air, a high proportion can be washed off using detergents or organic solvents. Stronger reagents such as EDTA or mineral acids may remove even more but run the risk of confusing the analysis by leaching out lead incorporated within the body of the hair.
The situation is different when hair absorbs lead in a mildly acidic aqueous solution. In this case it seems the lead ions are exchanged for ions from within the hair. The lead in this case is like a permanent dye and is not removed by the standard laboratory washing procedures.
In his memoir of the 1875 Arctic expedition, George Strong Nares wrote:
The greatest annoyance of all, and which has never yet been completely avoided in Arctic ships, was the moisture which collected on the beams of the messdeck, to such an extent as to necessitate their being frequently sponged in order to prevent it dripping.
Nares' ships didn't have the advantage of the Sylvester stove for heating the ship but there can be little doubt that condensation was an issue on Erebus and Terror.
The water condensing on the beams will have absorbed carbon dioxide from the air, creating carbonic acid. This mild acid will have leached lead from the painted surfaces of the beams. It may have dripped onto the men directly or been transferred to their hair as they wiped their fingers through it. The hair will have absorbed lead ions from the mildly acidic aqueous solution. The lead, tightly bound to the hair, would go on to confound scientists who were more familiar with the loosely bound hair-lead resulting from atmospheric pollution.
So, in short, my answer to the Franklin expedition lead question is paint. Lead paint on the candy. Lead paint on the ships.
My researches on the subject sparked a wider curiosity into the diet of the seamen of the era, which led me to start work on a simulation project. My plan is to live for one week solely on the seaman's diet of ships biscuit with either salted or canned meat on alternate days, plus the various other foodstuffs in the manifests. When I mentioned this to John Geiger he immediately replied "No! Do it for a year!". Well, we'll see.
As you can see in this photo, I already have most of the necessary stores assembled.