Hot houses
Reading Rick Jefferys’s letter on solar heating
(12 February, p 54) raises
the question: whatever happened to heat recovery systems for houses?
In the late 1970s, I visited a new development of timber-frame houses in
Washington, Tyne and Wear, in which heat recovery systems were installed. The
system consisted of a heat exchanger which extracted heat from outgoing air and
used it to heat incoming air. This was supplemented by electric heating. The
houses were also triple-glazed and the roof space, walls and floor were
insulated with 250 millimetre-thick rock wool. They were said to be very cheap
to heat.
Such a system combined with solar heating would be very fuel efficient, so
why has it not been more widely adopted? Perhaps someone could shed some light
on this?
Letter
Years ago as a childhood spaceflight enthusiast, I was enchanted that the
Army & Navy Stores book department displayed its astronomy books in the
travel section.
Correction
In the story “Latin America”
(12 February, p 7) we accurately
reported that a terracotta head found in Mexico had been confirmed by
anthropologists to be of Roman origin. However, the researcher mentioned in the
article is Romeo Hristov, not Roman Hristov as stated.
Grave slur
How dare you poke fun at our noble profession
(Feedback, 5 February). An
“anti-gravity check valve” is a device well-known to heating engineers. It is
used to prevent dense cold water moving under gravity to displace less dense hot
water elsewhere in a heating system鈥攁n effect which is always referred to
in the trade simply as “gravity”.
Really, you mustn’t make fun of things you don’t understand. Next you’ll be
smirking at our “cocks”, “nipples”, “balls” and “male” and “female” fittings.
Admittedly, it does take some explaining to the average 16-year-old apprentice
where the “2-inch iron cock” or “22-millimetre bleeding nipple” get their names,
but anti-gravity valves are probably the least funny thing in the job.
Plain truth
Your article about coffee was fascinating
(29 January, p 28), but according
to your graph, milk chocolate contains almost five times as much caffeine as
plain chocolate. I’m very curious to know why鈥攐r was this an error?
This was, indeed, a mistake. The two got inverted at some point in the
production process without our noticing. They should have been the other way
谤辞耻苍诲鈥抬诲
Rude science
Catherine Crick’s letter about finding New 杏吧原创 in the
“teenage” section of the magazine racks in W H Smith
(22 January, p 51) reminded
me of an incident one day in the early 1990s.
I was living and working in London, and having gone into a newsagents in
Sloane Square, I asked where I might find Nature magazine. The woman
behind the counter pointed to a row of what seemed to be mostly “adult”
magazines鈥擯enthouse, Playboy and the like. After a few
minutes of unsuccessful searching, I asked the sales assistant about New
杏吧原创.
“Beryl,” the woman called to her colleague, “do we keep Nude
杏吧原创?”
I was appalled, especially when my mind wandered to the possibility of a
centrefold.
Ageing crabs
Your report implies that working out the age of crustaceans from their neural
lipofuscins鈥攆atty hydrocarbon pigments鈥攊s a novel development by
Se-Jong Ju at the University of Maryland’s Chesapeake Biological Laboratory
(5 February, p 10).
The ability to age crustaceans is extremely important for fishery management.
This method of determining age was suggested by G. Ettershank as long ago as
1983, and in 1989 I showed that the approach worked for crustaceans, including
crabs.
However, the method may not be very accurate. Other studies have shown that
the unpurified fluorescent materials extracted from crustacean neural tissue by
Ju’s method are almost certainly not derived from lipofuscin granules in the
tissues, as they bear no quantitative relationship to them, or to age, only to
tissue sample mass and body mass. Where mass is broadly related to age this can
easily lead to misinterpretation of the results. Ju provides no convincing
additional evidence to the contrary.
Media for messages
I read your report on Mobe.Net, about a British network allowing customers to
use their mobile phone number as an e-mail address
(5 February, p 17). The
e-mail/short messaging service (SMS) gateway you describe is not new. Locust
(www.locust.net) has been running such a service for about three years now.
Cellnet has its Genie (www.genie.co.uk) service, which is free to all (if a
little slow), and even One2One has a service.
Many foreign networks have similar services. Locust will send multiple SMSs
for one e-mail and so get around the 160-character limit.
Our thanks to the many readers who have pointed out that other providers
offer this service鈥擡d
Letter
I suggest Richards forgets the possibility of cycle-friendly bumps and
attacks the problem by installing a spring-loaded saddle post. I have added a
commercially available model to my bike with excellent results.
Mutual attraction
In the article on “unlimited” energy
(22 January, p 32), the description of
the Casimir effect is very similar to Oliver Heaviside’s statement in
Electromagnetic Theory (vol 1, appendix B), which was published around
1900. Heaviside believed in the ether (zero-point energy). He writes: “Thus two
bodies which appear to attract are pushed together. The case of two large
parallel material planes exhibits this in a marked manner, for e [the
intensity of the force] is very small between them, and relatively large on
their further sides.”
To find further clues on how to extract energy from the vacuum, it could be
worthwhile revisiting the works of Heaviside.
Leg springs
In response to James Richards’s letter about speed bumps being uncomfortable
for cyclists
(12 February, p 55), I’ve yet to see a speed bump or rumble strip
that covers the whole road width, so they can usually be avoided fairly
easily.
Secondly, his comment about cyclists having no suspension is false. We have
the best suspension system available鈥攐ur legs. A simple answer is to take
your weight off your rear and onto your legs as you go over a bump. It works
perfectly every time, and can even stop jarring when you ride up the kerbs so
thoughtfully provided at the end of most cycle lanes.
Food imperialism
Oliver Morton’s example of vitamin A deficiency in Asia
(5 February, p 47) is
a particularly inappropriate example to use in support of GM crops. Vandana
Shiva tells in her book Monocultures of the Mind how traditional Indian
inter-cropping systems鈥攄eveloped to provide a complete range of foods for
local people鈥攚ere replaced by Green Revolution grain monocultures,
exported to the West for animal feed. As part of this process, the vegetable
bathua鈥攚ith its high vitamin A content鈥攚as eliminated as a
“weed”.
The result of such interference鈥攖hen, as now, under the rhetoric of
humanitarian aid鈥攊s that the regions of Africa, Asia and South America
where gross per capita food production has consistently increased over the past
20 years have also seen a consistent increase in malnutrition.
Shades of pale
The case of monkeys becoming “bleached” over generations
(5 February, p 32)
is perfectly consistent with natural selection. There is no need to invoke
orthogenesis鈥攖he theory that organisms are propelled along a predetermined
evolutionary pathway鈥攐r other esoteric ideas as explanations.
If it costs energy to make the pigment for coat colour, then in the absence
of any direct selection pressure, the less pigmented animal is better off.
Mutations that tend to colour loss will then be favoured over those enhancing
pigmentation, so an initially dark population will become lighter over time,
unless and until there is selection pressure in the opposite direction鈥攆or
protection against predators, sexual display, and so on.
That the world isn’t full of albinos shows that usually there is selection
based on coat colour. The gradual bleaching is nature’s default process in the
relatively few cases where this isn’t so.
Dropping shopping
Feedback’s item about Internet shopping
(5 February) struck a chord.
I too have been guilty of abandoning electronic shopping trollies without
buying anything. But there are a couple of other reasons for doing this you did
not mention. Postage and shipping charges aren’t always clear until you get to
the final stages of the purchase, and some sites insist that you give full
details of yourself even before you can view the online catalogue. So if, after
giving your Mickey Mouse name and Disney address to avoid receiving spam
e-mails, you actually see something you want to purchase, you have to abandon
your trolley and reconnect as yourself.
Maybe the designers of such sites should try to actually use their sites
before launching them on the unsuspecting public.