19th century artist and instructor John Ruskin founded a drawing school at Oxford University in 1871. Oxford has now posted his collection of images, notes and instruction into an immense
online catalogue. While much of the physical work has been dispersed around the world, the web allows the collection to be seen in its entirety, with information cross-referenced for ease of browsing. Oxford has also added contemporary interpretation of Ruskin's teachings, as well as short drawing instruction videos.
From the site:
He intended it not for the training of artists, but of ordinary men and women, who, by following his course, ‘might see greater beauties than they had hitherto seen in nature and in art, and thereby gain more pleasure in life’. His method required the student to master the rudiments of technique – outline, shading, colour – through a carefully directed course of lessons in copying both works of art and natural specimens.
Link:
The Elements of Drawing
Chris Oatley has a wonderful blog post about how to create realistic texture in digital painting by examining the techniques of the 19th century Hudson River School of painters. It's really important to open our eyes to history and see how past artists have tackled issues in visual image making and Chris has done a great job analyzing this particular period of realistic artists.