Spiral structure of galaxies. Drawings of spiral galaxies, published in 1850 by the Irish astronomer William Parsons (1800-1867), the third Earl of Rosse. The top drawing shows M99, while the bottom drawing shows M33. Lord Rosse had identified the spiral structure of M99 in 1846. He was the first to observe the spiral structure of these nebulae, later called galaxies, doing so in 1845 using his giant telescope, the Leviathan of Corkstown, in Ireland. For this work, Lord Rosse was awarded the Royal Society's Royal Medal in 1851. These drawings were published in the 1850 volume of Philosophical Transactions, the journal of the Royal Society, London, England.