Technique and condition
This lecture diagram on white wove Whatman paper shows four identical columns topped by an entablature, and the cast shadow of another part of the building. The basic structure consists of the four columns, the entablature and the blocks of the wall behind the colonnade marked in behind three of the columns: this composition is an upper copy of a lost original, as is Tracing of Guiding Lines (Tate D17132; Turner Bequest CXCV 161). Another copy from a similar original is Part of Classical Buildings, with Columns (Tate D17141; Turner Bequest CXCV 170).
Each column has been competed differently in brown and grey watercolour washes, to give an unrealistic view, while illustrating possible ways of depicting depth in an image of a building. The colouring implies that the two middle columns lie further back than the outer two. On the left side, this was achieved by using a graded wash on the leftmost column to illustrate its roundedness while leaving its more distant neighbour evenly coloured and less distinctive, and applying the deep shadow over both. On the right side, the nearer column has vertical fluting and the more distant one is plain (or indistinct) and must lie further back, since the shadow does not cut across it. In fact a pale grey shadow painted on at the correct angle implies shading from a more distant portion of the building. All these techniques depend on the artist’s ability to apply accurately an even wash with a hard edge (achievable with fairly dry paper) as well as a graded wash with no sharp transitions, which would be applied to wetter paper, without using so much water that the edge smeared out as it dried. The yellow/brown washes round the detailed structure show how less-controlled washes would be ineffective to depict depth, though even here Turner has – apparently effortlessly – indicated the cast shadow in the leftmost portion with a darker wash.
This work was made by a copying process which Turner used to generate a limited number of copies from other lecture diagrams. It is rare that all or even most stages of the process survive, and there is no complete set in the Turner Bequest, since these materials were presumably transported to and used for a number of lectures over the years. He needed several copies so that he could if he chose illustrate the drawing of a single element such as a column alone, then later with perspectival lines going to a single point, or built up to a colonnade of identical columns, or used to illustrate the way to make a smooth column look three-dimensional by shading. He could also use such a colonnade to form part of the elevation of a building, as in this example.