I discounted the telling on p156 because the population size (enough water for 8,000 people and 100,000 animals), the description of the tree (withered in the day and dropping at night), and being able to fill 20,000 tuns (about 1,000 L/tun) in a single day.
I also wonder how they were able to get the lead for those pipe. Other reports imply that there was little contact between the islands, so they likely didn't trade for all that material. Figure a 4 cm across, and 5 km of pipe gives 6 cubic meters of lead or 70 tons of lead, which is a full load on a Spanish caravel of the 1400s. And I think I'm underestimating that number.
I tried to find more historical information. The Spanish Wikipedia page points out that a well with brackish water was dug between 1702 and 1704, as part of a search to find drinkable water near the coast. It also commented that Columbus stopped there on his voyages to the Americas.
So I looked up a translation of the log of his first voyage. The entry for 9 Aug 1492 says:
> The Admiral says that many honourable Spaniards, inhabitants of the island of Hierro, swore that they were on Gomera with Dofia Inez Peraza, mother of Guillen Peraza, who was afterward the first Count of Gomera, and that each year they saw land to the west of the Canaries
"Many" is not helpful, but at least a few hundred people on the island?
I looked backwards in time. Jean IV de Béthencourt conquered the Canaries for Spain in the early 1400. "There was no resistance offered by the scattered guanche population who were largely sold as slaves" says Wikipedia. Nice guy.
Your best bet I think is to look for records in Spanish. Oh! I found "Conquista y antiguedades de las islas de Gran Canaria y su descripcion: con muchas advertencias de sus privilegios, conquistadores, pobladores, y otras particularidades en la muy poderosa isla de Tenerife", dated 1676,
Here's what I could copy from that text (updating the syntax to more modern Spanish):
La isla del Hierro esta diez y ocho leguas de Tenerife, es pequeña, tiene su Villa con buena Parroquia, y dos Beneficiados, que acuden a toda la isla y algunos Capellanes; ay vn Conaento de San Francisco; cogese much trigo, y ganado; rendra la isla mil y ochocientos vecinos, y muchos principales.
Here's my+Google's translation:
El Hierro is eighteen leagues from Tenerife, is small, has its Villa with good parish, and two Beneficiaries, who flock to the island and some chaplains; (also a convent of??) St. Francis; grows(?) much wheat, and cattle; the island (has?) 1,800 residents, and many (bosses? people who can represent your business interest?).
So, a 1670 population of about 1,800 people, under the Spanish crown, and before the 1702 well. I think this find greatly weakens the hypothesis that fog collection was necessary in order for a group of up to 2,000 people, and that they could have survived on the limited springs and cistern storage of rain water.
Sounds like the Bimbache people could support 4x the population that the Spanish could (8,000 vs. 2,000), which makes sense (water being the limiting resource in that landscape).
Why discount pp156 again? The numbers are perfectly doable with a carefully placed tree that uses the surrounding landscape to funnel fog to it.
Lead pipes wouldn't be needed for the entire length — clay-lined spillways would more than suffice. I read it as using lead just to the cistern.
Before starting, let me say that I've found this conversation very interesting. Thank you for participating in it with me.
I discounted it for several reasons.
1) There's no corroborating evidence that the population was that high. I haven't found anything more than "sparse", but http://www.sharprazor.com/palma-history.htm gives some of the history of La Palma:
> The Guanches named their island Benahoare, and divided it into 12 kingdoms, each with its own ruler. Estimates of the Guanche population at the time of the conquest range from 1200 to over 4000.
La Palma is over twice as big as El Hierro (708.32 km2 vs. 278 km2) and it seems to support better agriculture and easier access to the sea. I find it difficult to believe that the population density of El Hierro was at least 4x more than that La Palma, when the best I can find is that the population of El Hierro was "sparse."
2) The numbers I see for modern fog harvesting are about 5 liters per square meter per day. The account says that a tree could fill 20,000 tuns/day, which is about 20 million liters. This needs about 4 million square meters. Assuming an 80 meter high tree and 32 meters across (the size of a larger redwood tree) gives a cross section of 2,500 sq. meters. There's no way these numbers are close to compatible.
3) Let's assume the tree can capture an excess of 1 liter per sq. meter cross section, even though there's no evidence that any tree can do that. Let's assume also that a single tree has a cross section of 2,500 sq. meters. That's 2,500 liters per day. Not bad, but people need about 2 liters per day as a minimum - and more if they do much activity. Even in this unlikely and extreme case, that's only enough to provide basic water needs for 1,000 people.
The WHO says "a minimum of 7.5 litres per capita per day will meet the requirements of most people under most conditions", so that's 330 people. And no animals.
(Another estimate is to look at the amount of water in fog. A cloud has about 0.5 g of water/cubic meter. However, this is too complex for me to figure out, because I don't know how much water you can extract with fog mining, I don't know what a tree or other plant can extract, I don't the wind speed, and I don't know the capture area.)
4) Why use lead pipes to lead to the cistern? Since clay is good enough for the cisterns, what's the advantage of using lead for those pipes?
Since each individual detail is not trustworthy, I find it hard to put any faith in the overall account. How are you certain that it isn't a tall tale, with little to no basis in reality?
I also wonder how they were able to get the lead for those pipe. Other reports imply that there was little contact between the islands, so they likely didn't trade for all that material. Figure a 4 cm across, and 5 km of pipe gives 6 cubic meters of lead or 70 tons of lead, which is a full load on a Spanish caravel of the 1400s. And I think I'm underestimating that number.
I tried to find more historical information. The Spanish Wikipedia page points out that a well with brackish water was dug between 1702 and 1704, as part of a search to find drinkable water near the coast. It also commented that Columbus stopped there on his voyages to the Americas.
So I looked up a translation of the log of his first voyage. The entry for 9 Aug 1492 says:
> The Admiral says that many honourable Spaniards, inhabitants of the island of Hierro, swore that they were on Gomera with Dofia Inez Peraza, mother of Guillen Peraza, who was afterward the first Count of Gomera, and that each year they saw land to the west of the Canaries
"Many" is not helpful, but at least a few hundred people on the island?
I looked backwards in time. Jean IV de Béthencourt conquered the Canaries for Spain in the early 1400. "There was no resistance offered by the scattered guanche population who were largely sold as slaves" says Wikipedia. Nice guy.
Your best bet I think is to look for records in Spanish. Oh! I found "Conquista y antiguedades de las islas de Gran Canaria y su descripcion: con muchas advertencias de sus privilegios, conquistadores, pobladores, y otras particularidades en la muy poderosa isla de Tenerife", dated 1676,
My Spanish is rather poor, but I think page 59 of http://books.google.com/books?id=cKvrI2UF-LgC&pg=PA59&img=1&... says there were 1,800 inhabitants of El Hierro.
Here's what I could copy from that text (updating the syntax to more modern Spanish):
La isla del Hierro esta diez y ocho leguas de Tenerife, es pequeña, tiene su Villa con buena Parroquia, y dos Beneficiados, que acuden a toda la isla y algunos Capellanes; ay vn Conaento de San Francisco; cogese much trigo, y ganado; rendra la isla mil y ochocientos vecinos, y muchos principales.
Here's my+Google's translation:
El Hierro is eighteen leagues from Tenerife, is small, has its Villa with good parish, and two Beneficiaries, who flock to the island and some chaplains; (also a convent of??) St. Francis; grows(?) much wheat, and cattle; the island (has?) 1,800 residents, and many (bosses? people who can represent your business interest?).
So, a 1670 population of about 1,800 people, under the Spanish crown, and before the 1702 well. I think this find greatly weakens the hypothesis that fog collection was necessary in order for a group of up to 2,000 people, and that they could have survived on the limited springs and cistern storage of rain water.