Joseph Mallord William Turner, kown contemporarily as William Turner, was an English Romantic painter, printmaker and watercolourist. He is known for his expressive colourisations, imaginative landscapes and turbulent, often violent marine paintings. He opened his own gallery in 1804 and became professor of perspective at the Royal Academy of Arts in 1807, where he lectured until 1828. He left behind more than 550 oil paintings, 2,000 watercolours, and 30,000 works on paper. He had been championed by the leading English art critic John Ruskin from 1840, and is today regarded as having elevated landscape painting to an eminence rivalling history painting.