What is more, Rosand goes on to connect these exploratory features of the act of drawing to ways of seeing and knowing, especially as they are famously exemplified in the case of Leonardo da Vinci. Whether in the latter’s drawings of horses, his anatomical drawings, or the sketches made of whirlpools and locks of hair, one thing that becomes unmistakably clear, according to Rosand, is that «Leonardo’s mode of drawing is a mode of knowing» – something that was acknowledged by the Italian polymath himself. [8] In fact the very stylus and paper used, the pressures of the hand, and the quality and species of the line employed in a drawing may have all effected and influenced the way in which Leonardo might be said to come to see and know what was drawn. [9]

Whether in the case of Leonardo or in the case of our nebular observers; whether it was John Herschel standing before an Italian landscape with a pencil and paper in hand or at the eyepiece of a telescope, the following observation by Paul Valéry, a keen draughtsman himself and an aficionado of Leonardo’s drawings, is therefore apt: «There is a tremendous difference between seeing a thing without a pencil in your hand and seeing it while drawing it.» [10] It was this difference that was exploited by the observers of the faint, optically delicate, and unfamiliar nebulous objects.

In accord with the observational and epistemological potentials of seeing while drawing by hand an object, Barbara Wittmann has explicated a case in which a contemporary scientific draughtsman at the Berlin Museum of Natural History discovered through the act of drawing a specimen significant features of it that went entirely unnoticed by the scientist(s) for whom the drawings were made. [11] But notice, the draughtsman and scientist in this case are not one and the same person. This division between an hired artist and a scientist has its own history, as the work of Kärin Nickelsen has amply shown. Using cases from eighteenth century botany, she shows that many drawings meant for scientific purposes were a part of a process that divided the labor between the hands of a hired artist and the expert eyes of a scientist. [12] Daston and Galison have referred to this division in labor as a «four-eyed sight». [13]

Yet there is another entire category of scientific observer who draws for himself or herself; where eye and hand remain undivided. It was this category of observer (or observer-draughtsman) that Julius von Sachs wished to extol in his influential History of Biology (1875). In direct opposition to any perceived value of a four-eyed sight in the observations with a microscope, Sachs writes: