Form is always to be sacrificed to colour when both cannot be got in the time. If the colour is right in paleness or depth, the general result will of necessity include sound relations of light and shade, but these in their turn are more important in brush sketching than form.

Truth of detail is always, in a case of necessity, to be sacrificed to truth of mass. A blot, in right relations of tone and colour to the rest of the work, is better than a number of correct details out of tune.

Freshness is a greater virtue in a sketch than strict accuracy either in form, light and shade, or colour. A laboured sketch is naturally a spoiled sketch.

Inequality of work is not an evil in sketches. They may be detailed in one place, and in broad formless masses elsewhere, without inconvenience.

All executive defects, which are simply the result of speed, and not of ignorance, are perfectly admissible in sketches.

Keep your tools clean. Use cold water to put your brushes in; hot water softens them.

In oil painting some colours are naturally more opaque than others. Any of them can be made opaque by the admixture of white. The most transparent colours are madder lake, rose madder. brown madder, bitumen, and asphaltum. Antwerp blue and Vandyck brown are also transparent. Aureolin is a very brilliant, transparent yellow, but it is too costly for general use. Any oil colour may be made transparent by mixing it with sufficient clear oil. Poppy oil is very good for this purpose.