Royal Albert Dock, both in London, Dover harbour, and Valparaíso harbour in Chile. Soon after the Boxer Rebellion (1899–1901), the Moirs travelled through the interior of China to oversee the construction of a railway in Honan (Henan), even though Margaret had been refused a permit because of the presumed danger to a western woman of undertaking such a journey. She saw at first hand the hideous dangers experienced by workers in the caissons, the compressed-air chambers used in the construction of bridges: '[We descended] the ladders rung by rung until we got on to the working floor, the sea and liquid mud being kept out entirely by air that was continuously pumped from above.' The appalling death and injury rate from caisson disease (also known as the bends or decompression sickness) prompted Ernest Moir to invent and implement a 'medical air lock' for the recompression and slow decompression of those workers who were overcome when they arrived on the surface. In the case of the Hudson River Tunnel, this reduced the annual death rate of workers from 25 to 1 per cent. On completion of the Blackwall Tunnel in 1897, Margaret Moir became the first woman to walk under the River Thames from Kent to Middlesex. 'I then had to scramble up a ladder some 70 ft suspended in the air and come out of the air lock on the Poplar side,' she wrote later, acknowledging that she had not at the time appreciated the dangers involved. Following the Shell Crisis of 1915, and the consequent employment of huge numbers of women in munitions factories, Margaret Moir's empathy with working people prompted her to organise a relief scheme to give weekend respite to full-time workers; their places were taken by Lady Moir and her colleagues. She herself worked for more than 18 months as a lathe operator. She was treasurer and secretary of the Women's Advisory Committee of the National War Savings Committee, and she organised a sale of war savings certificates and war bonds in London department stores and at Victoria station, which reputedly raised several hundred thousand pounds. In recognition of her wartime work, in 1920 Margaret Moir was made an Officer of the Order of the British Empire (OBE). When the Women's Engineering Society was formed in 1919, Lady Moir was a founder member alongside Rachel Parsons, Lady Katharine Parsons, Eleanor Shelley-Rolls, Laura Annie Willson, Margaret Rowbotham