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As Jonathan Chenoweth reported, the water crisis is not a crisis of scarcity – yet – but a crisis of access, fuelled by weak international leadership (23 August, p 28) . There is enough fresh water but the poorest billion people are missing out: 1 person in 8 does not have access to safe water, …

Environmental scientists have long criticised economists' failure to address "externalities" – in particular their failure to account adequately for environmental and social impacts. Climate change at last seems to be altering economists' perspectives, as seen by the degree to which the UK's Stern report and Australia's Garnaut report are being taken seriously at a political …

The Siemens Intelligence Platform (23 August, p 24) does not carry out surveillance of the public, it only facilitates analysis of whatever surveillance is done, whether justified or not. That makes it a side issue. The real problem is the surveillance itself. When surveillance is carried to the point of injustice, as it is today …

Lawrence Krauss's commentary on the appearance of Christopher Monckton's piece on global warming in the newsletter of the American Physical Society's Forum on Physics and Society (16 August, p 46) could be read as implying that I should have warned the editors that Monckton is a controversial figure. To clarify the record, here is what …

I read with concern your article on "dark pools" in financial markets (26 July, p 24) . Do they not facilitate insider trading? Maybe "black market" would be a more appropriate term.

As my great-grandparents were friends and whist partners with Thomas Edison and his wife, his "Success is 10 per cent inspiration and 90 per cent perspiration" was a well-worn family saying. You attributed it to Einstein in your editorial (9 August, p 5) . Edison was also a purveyor of the idea that 15-minute catnaps …

Regarding your report on iron-containing superconductors (16 August, p 31) , the pedant in me can't resist pointing out that if power cables carrying superconducting currents really did waste energy by "humming along", they wouldn't be superconducting after all. From Fred Bortz Catherine Zandonella writes: "If you had superconducting circuits in your camera, you wouldn't …

Your article asking whether there is a connection between tornadoes and climate change (2 August, p 38) failed to mention one obvious factor: the ocean current pattern known as La Niña does appear to increase tornado activity. According to the US National Weather Forecast Service in Jackson, Missouri , of the top 15 US tornadic …

Diana Lutz's daughter spotted that the drug Pamprin – which is "for the temporary relief of symptoms associated with menstrual periods" – comes with the caveat that those with an enlarged prostate should seek medical advice before taking it (Feedback, 5 July) . She could be forgiven for thinking that Pamprin is aimed at men …

Alison Finch says she is sick of the slanging match between science and religion (9 August, p 20) . For many years I thought, like her, that it did not matter what others believed. I have changed my mind. Wherever we look – from the promotion of creationism in the US, to the war in …

Feedback's article on the strategy of charging a small deposit on containers to encourage recycling (16 August) reminded me of when my family took over the running of a newsagent's shop some 40 years ago. At that time lemonade and similar drinks were sold in glass bottles with a refundable deposit of 3 old pence …

Magda Sachs is absolutely right about the benefits to babies of banking breast milk (16 August, p 19) . Unfortunately this has become increasingly difficult to do due to the necessity of screening for diseases such as HIV/AIDS and pasteurising the milk. There is no profit in breast milk so no one is interested in …

Peter Aldhous reports how climate mapping can help plan biodiversity conservation (9 August, p 8) . It is already doing so in the UK: the RSPB has been involved in climate mapping projects for all of Europe's breeding birds and for species covered by the UK biodiversity action plan . The outputs from these projects …

David Weldon describes the failure of attempts to develop a "milk machine" around 50 years ago (23 August, p 21) . Progress since then should surely have made the job easier, for example, by creating genetically modified plants and designer bugs for processing them into milk. Since then, also, the need to reduce the environmental …

So the UK's Royal Mail Salisbury sorting office has a sign saying "Please Use Both Letterboxes" (Feedback, 12 July) . Is this not an experiment to examine whether postage is a wave or a particle? I predict that if they know where a letter is, they won't be able to tell you how long it …

• We stated that Alexandra Horowitz from Barnard College in New York believes that dogs have a "theory of behaviour" rather than a "theory of mind" (23 August, p 33) . She was merely pointing out an alternative explanation for some experiments in dog cognition: her own view is that dogs do have a rudimentary …