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Chicken or Egg? The Glevum Superior

The Glevum Superior, a two-storey paraffin-heated work of scientific art.

THE CHICKEN – and presumably its egg – was invented at least 8,000 years ago in the tropical forests of south-east Asia, where it went by the name of Red Junglefowl. As of 2023, there are a staggering 33 billion chickens  clucking, making them far and away the most populous birdbrain on the planet.

Humans love eating chickens. If you created a line, head to claw, of all the chickens eaten worldwide annually in KFC alone, it would circle the globe 11 times. Not surprisingly, few chickens live longer than 11 years although the Guinness World Records clocked one who died of heart failure when she was sweet 16.

One reason why there are so many chickens is that their eggs work very well. Indeed, given the right conditions, nearly all fertilised chicken eggs will hatch after 21 days. But, of course, us hungry humans have also had a major impact. By the 1890s, farmers had worked out that they could greatly increase the size of their flock if they took over the hatching process. Combined with selective breeding, this ensured that average egg production per hen jumped from 83 eggs per year in 1900 to well over 300 per year in the present century.

The key tool for this seismic eggsplosion was the artificial incubator. One of the earliest was the Glevum Superior, a two-storey paraffin-heated work of scientific art built in Gloucester. The one photographed above lived in a shed near Clones in Co Monaghan, one of Ireland’s poultry breeding epicentres.

The concept is straightforward. Eggs are whipped out from beneath the broody bantams, placed on a tray and sent into an incubator which is fixed to the right temperature and humidity conditions.

The Glevum could take up to 150 eggs at a time. If the eggs weren’t rolled every now and then, some would get too hot, resulting in unretracted yolks, malpositioned chicks and other problem hatches. A well-practiced keeper would simply remove the tray, sweep a hand through the eggs with a circular motion, reverse the tray and replace it.

It’s not a whole lot different to how Mother Hen treats them, randomly shuffling the eggs about with her beak every time she settles down again. The results obtained by a skilled keeper were every bit as good as those obtained today by the Glevum’s electric, automatic, programmable successors.




This article originally  featured in the ‘Curiosities’ column in The Irish Times Magazine, Saturday 23 August 2008.