Letters: Sand test
I was interested to read your article ‘Fake leaves spot thirsty plants’
(Technology, 2 July). It is certainly another scientific tool to provide
information for decisions about irrigation. There are less scientific methods;
one is to mix sand in the soil of a few representative plants. The sand
reduces the water-holding capacity of the soil and these plants then feel
the effects of water shortage first and give the farmer early warning of
the stress on the other plants.
Neil Redwood Melbourne, Australia
Letters: Igloo to you
What does an igloo do (Letters, 6 August)? Despite being made of a cold
material, it keeps the interior warm by virtue of the low thermal conductivity
of the material of which it is made. It keeps off the wind chill by being
impermeable. What has all this got to do with global cooling? Nothing. Please
don’t let’s coin a phrase with nothing more to recommend it than a similarity
to another phrase that means something.
‘The aerosol effect’, as used in Fred Pearce’s article (‘Not warming,
but cooling’, 9 July), is accurate. If you want an analogy with greenhouses
then think of the silvered glass of office buildings – the ‘reflective
tinted glass effect’ perhaps. No, maybe it wouldn’t catch on. But not igloos.
Please.
Hugh Dukes Luton, Bedfordshire
Letters: Correction
In the article ‘Should the cat take the rap’ (21 May), the illustration
of a cat gorging itself on Australian animals was attributed to John Allison.
In fact the picture was by Kaye Kessing, and we would like to apologise
to Ms Kessing for the error.
Letters: SuperBritish
David Bradley’s article on supercritical fluids (‘Solvents get the big
squeeze’, 6 August) gave a valuable insight into this increasingly important
area of physical chemistry but for one major omission – there was no mention
of Europe’s largest research group working on SCFs which is based here in
Britain. Headed by Keith Bartle and Tony Clifford, the Supercritical Fluids
Group at the University of Leeds has been researching SCFs for over ten
years and now numbers more than thirty full-time researchers.
The traditional exponents of SCF technology have been related to the
food industry. Decaffeination of coffee and the extraction of essential
oils and flavours are well known but the next major breakthroughs are likely
to be in the pharmaceutical industry. Not only are SCFs being used as an
alternative to organic solvents in a variety of extraction and analytical
processes, but we are currently using them in new methods of drug formulation,
the preparation of sub-micron-sized particles and new methods of coating
fine particles with polymers for controlled release.
Other novel applications currently under investigation in Leeds include
the separation of chiral molecules, again a pharmaceutical use; heavy metals
separation and extraction; and, as the article briefly described from a
US perspective, toxic waste destruction. Incidentally, Clifford is currently
a scientific advisor to the NATO and US Army select committees on the destruction
of chemical weapons and propellants by the use of supercritical water.
With such an array of uses for SCFs, physical chemistry looks set to
go supercritical.
Derek Riley Leeds
Letters: Streaks ahead
Feedback (30 July) is quite right to point out Britain’s lack of involvement
in space, but the government’s attitude can be traced back to the mid-1960s
when the then Labour government cancelled Britain’s great hope for the future,
Blue Streak.
Blue Streak began life as Britain’s attempt at acquiring a nuclear
deterrent based on an intercontinental ballistic missile, but in a very
short period of time it became apparent that liquid fuel rocket systems
had major drawbacks in the military arena. Geoffrey Pardoe presented a paper
in 1959 – the first public admission that the missile existed – which suggested
that Blue Streak could be used as the first stage of a satellite launch
vehicle, with Black Knight as the second stage and a military solid fuel
rocket as the third stage. It would have been capable of putting a 1-tonne
satellite in orbit. The reaction from government at the time was very negative.
There can be little doubt that the country missed out on a huge opportunity.
Cancelling Blue Streak left the field open in Europe for the French, who
have capitalised on their position. But they’ve never matched the promise
of the British vehicle. As Ray Hancock, a liaison engineer now retired from
Rolls Royce, says, ‘The French occasionally keep dumping a satellite in
the middle of the Atlantic. The Americans have their Atlas failures even
now. We didn’t’. Blue Streak carved a special niche for itself in history
as the most reliable space vehicle there has ever been. In the course of
11 launches it suffered not a single failure, and remains a testament to
the brilliance of the British engineers who created it.
Border Television will be screening a documentary on Blue Streak on
5 December.
Ian Fisher Border Television Carlisle
Letters: Save the wartbiter
Andrew Lucas implies that, in choosing which rare species to save,
most effort is concentrated on flagship animal species rather than on undistinguished
invertebrates and plants (Forum, 6 August). Certainly the choice is difficult.
In Britain, there are well over two thousand plants and animals listed as
endangered or vulnerable in British Red Data Books and some 300 of these
are specially protected by the Wildlife and Countryside Act 1981. But choose
we must.
Since 1991, English Nature has undertaken a species recovery programme,
with the short-term objective of reversing the decline in the populations
of threatened species and a longer-term objective of establishing self-sustaining
populations of these species in the wild.
Through this programme we are presently supporting work on 50 species
of plants and animals, 30 being full recovery projects. Some have familiar
names such as the lady’s slipper orchid, cornflower, dormouse, red squirrel,
bittern, large blue butterfly and swallowtail. However, we also champion
the more obscure, such as the wartbiter, stinking hawk’s beard, thistle
broomrape, strapwort, shore dock, ladybird and fen raft spiders, cicada,
barberry carpet and reddish buff moths, spangled water beetle, glutinous
snail, lagoon sand-worm and, yes, that Dorset ant as well. While we have
not yet included the black rat in our programme, work is about to start
on the pine marten which is considered equally repugnant by some.
Yes, value judgments do play a part, but we would be rightly criticised
if we ignored well-known species; surely, they too deserve their chance
of being brought back from the brink of extinction. We purposely take into
account that such species have the distinct advantage of attracting sponsors
as well as helping to focus public understanding and appreciation of the
requirement for species conservation.
This is not a ‘quick fix’ programme centred solely on single species.
Much of the action is in managing the habitat to improve conditions for
a range of species, whether notable, nondescript, nice or nasty.
Roger Mitchell English Nature Peterborough
Letters: Self-fulfilling
The National Road Traffic Forecast produced annually by the Department
of Transport predicts that road traffic will increase in Britain by between
69 and 113 per cent by 2025 (This Week, 13 August). However, I question
the validity of the forecast, which is calculated as an extrapolation of
the current rate of increase in road traffic.
It has been argued since the early 1970s that road building generates
new traffic, which increases to fill the road space available as a result
of easier and cheaper travel.
The traffic forecast is used by the Department of Transport to assess
the economic viability of new road schemes, yet it ignores the increasingly
likely possibility that the current rate of traffic increase is directly
correlated with the government’s multibillion-pound road-building programme.
The doubling of traffic, far from being inevitable, is dependent upon new
roads continuing to deface our countryside and heritage at the current rate.
To use the forecast as justification for building those roads is a spurious
and circular argument.
Lynn Hunt University of Oxford
Letters: Ethical hypnosis
Your contributor Phil Bagnall alleged that clinical hypnosis was a ‘dubious
science’, implying it had little therapeutic value beyond helping smokers
quit their habit (Forum, 30 July and Letters, 27 August). He would appear
to be unaware of the substantial body of research published on the therapeutic
benefits of hypnosis.
Over the past few issues, the European Journal of Clinical Hypnosis
has published papers on the effects of psychological intervention on patients
with inflammatory bowel disease; examined desensitisation in the treatment
of phobias; carried the results of trials on the use of hypnosis in normal
labour, published new conclusions on its use in dealing with erectile dysfunction,
and research findings on the effectiveness of hypnotherapy in medically
unexplained, functional and psychosomatic infertility.
Almost all will share and understand the concern felt about the emergence
of the so-called ‘false memory syndrome’. Unfortunately, the FMS debate
is in danger of being dominated by two opposing but equally polemic camps
and Bagnall risks falling into one of these camps. On one side are those
who are convinced that just about every personal problem arises from childhood
sexual abuse. On the other are those who deny that recovered memories of
forgotten abuse can be genuine.
Neither stance represents the truth. In its last two issues, our journal
has carried well balanced, objective reports tracing the rise of this debate
and examining the danger that expectation of abuse may have become fashionable
among some therapists. Maybe Bagnall would be surprised to discover what
is the attitude of the majority of experienced – and I would say, highly
ethical – hypnotherapists towards this highly charged issue.
W. H. Doult European Journal Of Clinical Hypnosis London
Letters: Aeroplane aerosols
It is difficult to understand why no mention was made of the effects
of aviation on the atmosphere in Fred Pearce’s otherwise excellent article
on the effects of aerosols on the earth’s climates (‘Not warming, but cooling,’
9 July).
Air traffic has increased enormously over the past fifty years with
no end in sight. Aircraft engines distribute their combustion products
in the lower stratosphere and upper troposphere and can be considered direct,
point sources of pollution guaranteed to produce maximum change.
Water vapor (contrails), soot, sulphate aerosols, all mentioned by Pearce
as contributing to the worrisome atmospheric change, are all produced by
aircraft. In discussing power plant emissions and the height of chimneys,
he writes, ‘. . . contaminants are spread into the higher levels of the
atmosphere, where they can more readily interact with clouds’. This would
certainly hold true for the heavily travelled North American-Northern Europe
commercial air corridor and elsewhere.
It is worth considering that the dynamic imbalance of the cooling effects
of aerosols on the northern hemisphere and the absence of cooling on the
southern hemisphere might also be paralleled by these aerosols absorbing
increased ultraviolet rays from depleted stratospheric ozone in the north
and not in the south. Is the south being differentially warmed and irradiated?
We won’t know until someone looks.
Jim Scanlon San Rafael, California