But you will no doubt say the model moves, and this shifting of the face makes you uncertain. I can sympathise with you, but to make certain, let the space beyond the point of the nose be your guide.
Plate XIV. may help you to realise this aspect; but you should study this problem at first hand from nature. The upright edge of the book indicated assists one to fix the curves and tendency of the lines of the face.
It is well-nigh impossible to generalise about the form of so varying a feature as the nose ; but after studying its anatomy it would be well to consider it in its relation to the mouth, noting particularly in the construction of that part of the face that the centre of - the upper lip falls, whichever way the head is turned, under the centre of the nose, and that the central marking between the two cushions of the lower lip lies under the central dip of the upper.
Plate XV. shows two views of the mouth in what is usually a difficult foreshortened aspect of the feature to realise.
The beginner should take care to avoid the all too frequent error of drawing on the three quarter face a nose seen too much in profile.
All solid masses have their "beyond" The power to make one realise that there are planes unseen is of the very essence of good draughtsmanship, and in this connection I would draw your attention to the need of care to trace the flow of all lines that are intercepted.