Autograph Letter Signed, to William Gourlie jnr, welcoming him as a subscriber to the History of the British Freshwater Algae, offering to send the Prospectus to his friends, 2 pp. 7 x 4½ inches, in good condition. Addison Road North, Notting Hill, 5 April 1844. Arthur Hill Hassall (1817 – 1894) was a British physician, chemist and microscopist who is primarily known for his work in public health and food safety. In 1846 he published a two-volume study, The Microscopic Anatomy of the Human Body in Health and Disease, the first English textbook on the subject. After further studying botany at Kew and publishing on botanical topics, particularly freshwater algae, he came to public attention with his 1850 book ‘A microscopical examination of the water supplied to the inhabitants of London and the suburban districts’, which became an influential work in promoting the cause of water reform. In the early 1850s he also studied food adulteration; his reports were published in The Lancet by reformer Thomas Wakley and led directly to the 1860 Food Adulteration Act and subsequent further legislation against the practice.