Captain Back's Patent Poison Producer

This bizarre contraption is my home-made experiment intended to shed some light on the question of the origin of the lead detected in the bones of participants in the Franklin Expedition. The apparatus is designed to  approximate the system originally installed on HMS Terror following the suggestion of Captain George Back on the 16th of May, 1836. A 2kw wallpaper steamer plays the part of the Fraser stove and the condenser/snow-tank is a black plastic box which normally holds paper for recycling. The five-foot length of lead piping between them is arranged so that any water condensed within it can't flow back into the steamer but instead drains via a narrow plastic tube into a glass jar on the floor. This approximates the arrangements shown on the 1837 profile drawing of HMS Terror but has the advantage, for experimental purposes, that the water which condenses in the pipe can be collected separately instead of mixing with the boiler water. 

I had been worrying how to test the lead content of the water produced. There are test strips available, for a few pounds, which give a yes/no answer to the question of whether lead is present in tap water and there are digital colorimeters, costing a few hundreds, which give an accurate measurement in terms of parts per million. In the event, no special equipment is needed. The water collected is cloudy with lead carbonate - white lead. After an hour or so the water clears leaving a powdery deposit at the bottom of the jar. When the jar is shaken it produces a pretty snow storm of glinting crystals, as shown by the middle one of the three jars in the photo above. This sample was produced as the result of 30 minutes operation. The conclusion I draw from this demonstration is: that the water making systems in place on Erebus and Terror during the fatal 1845 Franklin Expedition are likely to have introduced relatively huge quantities of lead, measurable in terms of grams per day, into the drinking water supplies, when the ships were overwintering. This seems likely to have been the major source of lead exposure, totally overwhelming any trace amounts absorbed from any other of the proposed sources.

Time we put the tinned food back in the cupboard: Busting the Franklin Expedition myth of 'lead poisoning from tinned food'.

The idea that Franklin's men were poisoned by lead from tinned food has reached almost the status of dogma. For many members of the public it seems to be almost the only 'fact' they know about the expedition.

Owen Beattie and John Geiger's bestselling book 'Frozen in Time' (2004 edition) includes the statement "There is no question of the source of the lead found in the bodies of Franklin's men: it came from the tinned foods". This claim is supported by a paper by Walt Kowal and others published in the Journal of Archaeological Science in March 1991, but, contrary to that claim, the source of the lead was questioned from the very first.

ISOTOPES:

Kowal and his co-authors found that the ratios of the several isotopes of lead in solder from cans found on Beechey Island matched the ratios measured in human remains from Beechey and King William Islands. They concluded from this that the lead in both cases came from the same source. That seems reasonable - indeed it's likely that all the lead on the ships came from the same source.

No measurements were made on contemporary British samples of lead, instead the authors referred to a database of isotope ratios of 98 samples of lead ore from the British Isles published by Stephen Moorbath in 1962.

Having found no credible match, they speculated that:

"...since the isotopic ratio for the Franklin materials is so different from most lead sources in the British Isles, it is quite possible that the lead used in the solder manufacture came from some other nation".

Their argument seems to be, that because all of the other sources of lead which the members of the expedition would have been exposed would have come from British mines, then the only possible explanation for the presence of the unusual exotic lead in the human remains was that it had come from the solder of the tin cans.

Unfortunately mass-spectrometry was still in its infancy in the early sixties, and the isotope measurements published in Moorbath's paper do not bear direct comparison with those made thirty years later. In 1996 Brenda Rohl published isotope ratios of 383 samples of lead ore from the British Isles. Her introduction states:

"The data in pioneering papers such as Moorbath (1962) and Brown (1966) are now too inaccurate to be compared with modern lead isotope data".

MINING:

It is implausable that isotope data could be used to trace the origin of any industrial era lead back to a single mine. Even connecting a sample with a single mining region presents difficulties.

Veins of ore with distinct isotope ratios can occur in close proximity. Equally, veins with indistinuishable isotope signatures can occur many miles apart. A small number of smelters would serve numerous mines within a region, producing metallic lead with an isotope signature averaged from the constituent ores.

Lead is probably the most easily recycled material known to man. At the lead mills ingots of newly smelted lead would be melted together with old lead scrap to manufacture whichever products the market required, such as sheet or pipe or solder.

The isotope signature of a typical sample of manufactured lead would therefore represent an amalgam of both contemporary and previously active mining regions. The average composition of the mixture would change only gradually as established mining regions declined and new ore provinces were exploited.

In 1839, Andrew Ure published statistics showing the relative productivity of the different Lead mining regions at that time. The North Pennines (Durham, Cumberland, and Yorkshire) being the dominant region.

Click on image for source document

The following chart compares the Franklin project data with geological data from Rohl, chosen with reference to the above table, and data from 36 samples from the Northern Pennines, from a 2001 paper by Brett Scaife and others.

Click to enlarge.

Data points from the two Welsh counties are represented by the larger circles to make up for their small number. Derbyshire had been of greater significance in the preceding century hence may deserve greater prominence than Ure's figures suggest due to recycling of old lead. There has been no attempt to distinguish the relative productivity of individual mines within a region, nor to represent measurement confidence intervals.

The main feature to note in the above chart is that all the data points for the Franklin samples are within the locus of the data points for the Northern Pennines.

CONCLUSION:

It is plausible that the isotope signature shared by both the solder and the human remains is simply that of common English lead of the period and that the high levels of lead detected in the human remains could have resulted from exposure to any of a myriad of contemporary sources and certainly not uniquely to the solder of the tin cans.

That members of the expedition suffered from lead exposure is not disputed, but there is no evidence to suggest that "it was the reliance of Franklin's expedition on tinned food that was the root cause".

The supplier of the tinned food, the much vilified Stefan Goldner, is exonerated of any blame in connection with the demise of the Franklin Expedition.

The eminent Food Scientist and Science historian Keith Farrer, OBE (who even has an award named after him) was among the first to question the 'lead poisoning from tin cans' hypothesis.

In a paper published in the Journal of Archaeological Science in 1993, Farrer pointed out, among other things, that only acidic foods such as tomatoes can defeat the cathodic protection conferred on lead by the more reactive tin and iron and that the canned provisions supplied to the expedition included no acidic component. It appears that all published reports of canned food being been found with a high lead content have involved acidic foodstuffs.

Farrer's conclusion regarding the canned food was that "their contribution to the body loads of lead or to any incipient ill health in Franklin's crewmen was trivial".

However no scholarly article in a scientific journal can compete for the public consciousness with a bestseller like 'Frozen in Time'.

So I hope this small effort does something to redress the balance.

01-Aug-2011

George Back, saviour of Franklin's first expedition, unwitting poisoner of Franklin's last expedition

As a member of the first Arctic expedition commanded by Captain Franklin, the overland "Journey to the shores of the Polar Sea", Midshipman George Back made two courageous life-saving journeys, which prevented that expedition from becoming a complete tragedy. It is therefore ironic that it seems that Back may have later played an unwitting hand in adding lead poisoning to the misfortunes of the final, fatal, Franklin Expedition.

In my previous post I suggested that Sir Edward Belcher may have been responsible for installing the sub-standard snow-melters in the Erebus and Terror. I now find I have to eat my words as it appears the arrangement was finalised after the then Commander Belcher hauled down his pennant on the Terror on March 24 1836.

Belcher had modified Erebus and Terror in preparation for a mission to relieve a whaling fleet beset in sea ice off Greenland. In the event James Clark Ross conducted that task in the Cove, a hired whaler, so the Admiralty decided to make use of the Terror on a mission to trace the Northern boundary of the North American continent.

George Back was high in the Admiralty's esteem because of his recent success in his overland expedition to the mouth of the Great Fish River in 1833-35. He was promoted to Captain within a month of his return and was appointed to command the Terror on May 13th 1836.

Some rummaging in the National Archives last weekend produced a couple of letters which throw new light on the story of the ships' galley stoves and their attached snow-melters. The letters are both from Captain Back to Charles Wood, First Secretary to the Admiralty.

National Archives, Crown copyright waived for non-commercial use.

May 16th 1836

Sir,
I have the honor to inform you that the fire-hearth or galley apparatus of the Terror is fitted for a crew of 260 men, and in order to save fuel, I would suggest that a fire-hearth or grate of Williams, similar to that now in the Blazer be placed in its stead.

A note scribbled on a corner records the decision:

National Archives, Crown copyright waived for non-commercial use.

May 16. Store-keeper Genl to furnish one of Frazer's firehearths fit for a crew of 60 men

A second letter highlights a problem with the installation:

National Archives, Crown copyright waived for non-commercial use.

May 20th 1836

Sir,
The first Lieutenant of the Terror having represented to me that there is no scuttle over the condenser for the purpose of throwing in snow to melt, I have to request that you will move the Lords Commissioners of the Admiralty to give the necessary directions.

So what does this mean?

Back's suggestion to save fuel by replacing the over-sized galley stove was a good one. However, working under time pressure to get the Terror ready for the Arctic, the dockyard workers made mistakes. Lieutenant Smythe noticed the lack of a scuttle but other mistakes were overlooked and seem to have had unfortunate consequences.

The workmen who installed the ice tank appear to have thought of it only as a condenser for the steam of the cooks coppers and they were unaware of its additional intended duty of melting snow for water.

If, as seems likely, the pipe (shown on the Terror's plans) connecting the coppers and the ice tank was made of lead, it would have been made in Chatham's Lead and Paint Mills which since 1818 had produced all the Navy's lead products.

Clem Rutter, Wikimedia, CC BY-SA 3.0

Brass or Copper would also be a possibility although in the absence of seamless tubing, which would not be patented until June 1838, crafting such a curved pipe in the time available would be a fine test of the coppersmith's art. The end result would necessarily include many soldered joints.

It would therefore seem to be a reasonable explanation for the observed evidence of lead poisoning on the Franklin expedition that the lead came from the steam pipe fitted between 16th and 20th of May 1836 on the Terror, and from its duplicate on the Erebus. The lead being transferred to the ships' potable water by cycles of cooking and snow melting in the ships' coppers. There are of course many possible explanations (tinned food not being among them), but this has the advantage of having as it's cause something we can point to on the ships' plans instead of being dependant on suppositions unsupported by evidence.

So it seems likely that George Back played an unwitting role in the addition of lead poisoning to the list of hardships endured by Franklin's men. It is a final twist of irony that, after the ships were abandoned, the retreating party sought safety by heading for the river which was the source of Back's fame and which bore his name.

Did Edward Belcher poison the Franklin Expedition?

Captain Sir Edward Belcher led the final government sponsored Franklin search expedition of 1852-54.

Les well know is the fact that, during the winter of 1835-36, the then Commander Belcher oversaw the fitting out of Erebus and Terror for service in the polar seas. Years later he reminisced about the Perkins heating system he had installed on the Terror even though, unbeknown to him, it had proved a failure on Back's 1836 voyage and was apparently dismissed as expensive quackery by Sir John Barrow.

I would love to have titled this post "I accuse! - Edward Belcher, with the Lead Piping, at Chatham Dockyard" but as I am still sifting the evidence of changes after Belcher's involvement we have to give him the benefit of the doubt.

The above image is my interpretation of the arrangement of galley stove (colloquially "the coppers") and ice tank installed in 1836, mostly based on details from the 1837 profile of HMS Terror in the National Maritime Museum. I have assumed four boilers (also "the coppers") each with a separate drain cock although the original drawing shows only one over-large tap at the back of the stove. I think it likely that this arrangement continued in use on both Ross and Crozier's 1839-43 Antarctic expedition and the fatal 1845 Franklin Expedition.

William Battersby originated the suggestion that the source of lead poisoning on the Franklin Expedition was the water making system installed on the ships. I consider his suggestion of lead for the material of the connecting pipe (shown in red) between the Fraser stove and the overhead ice-tank to be of particular significance.

As far as I know, the only account of this system in use is found in the journal of Royal Marines Sergeant William Cunningham of HMS Terror. It is instructive to compare some entries for 1841 in that journal with corresponding accounts in the ship's log.

5 Feb: Thawing Ice in the Coppers all day and night:

[7 Feb: Rec'd in the tanks 750 galls of water from the ice]

13 Feb: Large pieces of Ice falling from the Ropes aloft which gathered up and put in the Ice Tank for Thawing.

[16 Feb: Received 70 Gallons water made from the ice]

The relative quantities and timescales of these two examples suggests to me that the primary means for water making on these ships was not the ice tank but, as on Parry's first voyage, the coppers.

Cunningham's entry for 25 March mentions both the ice tank and the coppers:

Got the ice tank down from over the Cooks Coppers and a funnel Shipped on the scuttle which will carry the Steam off the Lower deck and thereby make it much comfortabler and wholesome for everyone.

By 20 December 1841 they'd discovered an easier way to complete their water:

Made fast to a Floe of ice & filled four tanks with beautifull fresh water ice.

Parry's ships from his second voyage (1821) onwards each had a "simple ingenious and effectual contrivance" which melted snow using waste heat from the stove's flue. Apparently the same apparatus also condensed the waste steam from cooking. The ships of the searching expeditions were also equipped with comparable systems. The plans of the search ships Enterprise and Investigator at the National Maritime Museum show arrangements very similar to those installed on Erebus and Terror with the exception that the ice tank extends further forwards with the stove's flue passing up through it to transmit waste heat to its contents. No steam pipes are shown but unless they were happy to have the galley dripping with condensation then they must have been fitted. The unique feature of the ice tanks of Erebus and Terror was that their only connection to the coppers was by the steam pipe. I would expect them to have been efficient condensers but poor ice-melters.

It is very wasteful of energy to cook with the water continually boiling instead of simmering or as James Fitzjames puts it "just not boiling". It also serves no purpose making significant amounts of steam when reheating canned food to serving temperature.

Considering the extra fuel needed to make sufficient steam and the heat lost to the air, I'd make a rough guess that making water by melting snow in the coppers would require around half the energy needed to make a similar quantity in these ice tanks. So I'd say it would be a logical assumption that on the Franklin Expedition at least some of the water was derived from snow melted in the coppers instead of in the ice tank in order to minimise expenditure of fuel.

Looking again at diagram of the galley it is not difficult to imagine how the water produced in this way could become contaminated with lead.

When the stove is being used for cooking each boiler holds a kettle of provisions which is heated by the boiling water on the bain-marie principle. Excess steam from the cooking rises up the pipe to the ice tank but much of it condenses on the walls of the pipe and runs back down, dissolving lead from the inside of the pipe as it does so and contaminating the boiler water.

When cooking duties are completed, the kettles are removed from the boilers and, oblivious to the possibility of contamination, blocks of snow are loaded into the boilers for melting into water. No steam is generated in water making. The contamination is caused by the repeating cycle of cooking and snow-melting without cleaning out the boilers in between.

The water first drawn from the boilers next to the steam pipe would be the most contaminated while the water from the boilers on the other side would be pure.

The ships which preceded, and those which followed, Erebus and Terror never needed to melt ice in their coppers because their ice tanks produced abundant pure water, at no energy cost, using waste heat. It would not matter if the water in their cooking boilers did become contaminated because that water would never be used for human consumption, simply topped up as it evaporated.

This then is my explanation for the lead poisoning on the Franklin Expedition and my suspicions as to the culprit.

Innocent until proven guilty, of course.