Question: when is a cannon not a cannon? Answer: when it’s a ‘high-pressure long-range deodorant spray’(!). For such is the description of the cannons currently being deployed in China to combat the malodorous odours emanating from a Beijing rubbish dump (http://news.bbc.co.uk/1/hi/world/asia-pacific/8639248.stm). Over 100 of the odour-busting devices have been recruited to defend the city’s inhabitants from the offensive smells that issue forth from the Gaóantun landfill site. In a nice twist the offending odour – due in no small measure to decaying plant matter – is being neutralised by dousing with a spray made from… plant extracts. But, try as I might, I could not sniff out the precise formulation of this mixture for you.