Origins of the bonfire; beware the garden rabbit menace; is the human body an efficient machine?

Why is it a "bonfire" rather than "fire"?

Just as some religious festivals were grafted on to existing calendar events – eg Christmas superseded the pagan festival of Sol, or the winter solstice – the creation of Bonfire Night was a propaganda exercise that was grafted onto an annual event in the agricultural calendar.

As the growing season effectively comes to an end around the beginning of November, farmers would prepare to eke out their winter fodder by slaughtering most of their animals, keeping only breeding pairs with a view to replacing their stock the following spring. Having preserved the meat, rendered the fat and treated the hides, they were left with the carcasses. In order to convert these into fertiliser, they had to be burned on a "bone fire", shortened over time to "bonfire".

The propaganda exercise proved so successful that Bonfire Night continues to be celebrated more than 400 years after the event, even though both the event it commemorates – the execution of Guy Fawkes – is now highly un-PC, and the annual ritual of "bone fires" has long since faded out of practice.

Bill Finlay, Aspatria, Cumbria

The word derives from the mid-15th century word "banefire", originally a fire in which bones were burned. Dr Johnson mistakenly derived it from the French "bon" (good).

Nader Fekri, Hebden Bridge, West Yorks

How can I stop my neighbours' cats from relieving themselves in my vegetable patch?

Regarding the discussions about cats and rabbits (N&Q, 4 November), a friend of mine moved into a house with a large garden some years ago and wondered why there wasn't much growing in it. The answer came when he looked out early one morning and saw that the garden was full of rabbits. He solved the problem by aquiring two cats, which rarely needed feeding as they were full of rabbit.

Not having a rabbit problem, I find that criss-crossing canes or similar over my vegetable beds discourages the cats, as does the netting, fleece etc I put in place to keep out insect pests and birds. There's always something trying to benefit from your best efforts.

Clint Backhouse, Carlisle

How efficient is the human body as a machine that turns food into energy?

This partly depends on how efficiency is defined. Respiration, the process of turning chemical or food energy into usable energy, is 38% efficient (this is the percentage of chemical energy available from glucose oxidation that is converted into the chemical energy of ATP – adenosine triphosphate). Like an endless procession of porters, each molecule of ATP carries a little parcel of energy to where it is needed. The remaining 62% of energy manifests itself as heat. This explains why we are warm.

This energy is not wasted, as being warm-blooded bestows advantages that may revise the efficiency figure upwards. However, of the 38% available to the cells, half is "wasted" in physical exercise, reducing the overall efficiency to about 20%. But it depends on who is doing what activity: for example, endurance cyclists with slow twitch fibres tend to be more efficient than those with fast twitch fibres.

Efficiency also varies between different tissues or organs. Compared to other tissue, muscle wastes more energy as heat. Given that men are generally more muscular than women, this is the physiological explanation of why women generally feel colder than men. Proof, if any were needed, that men are less efficient.

Mike Follows, Willenhall, West Mids

Any answers?

How do zombies know not to eat each other? What would they do if there were no non-zombies left?

Renee-Margaret Slater, Aberdeen

Why is it rashers of bacon, but slices of other meats?

Jane Simpson, York

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