A good conductor, interpreting the thought of the composer, does twenty things at once: reads the score, waves his baton, watches the singer, makes a motion sideways, first to the drum then to the wind-instruments, and so on. I do just the same when I lecture. Before me a hundred and fifty faces, all unlike one another; three hundred eyes all looking straight into my face. My object is to dominate this many-headed monster. If every moment as I lecture I have a clear vision of the degree of its attention and its power of comprehension, it is in my power. The other foe I have to overcome is in myself. It is the infinite variety of forms, phenomena, laws, and the multitude of ideas of my own and other people's conditioned by them. Every moment I must have the skill to snatch out of that vast mass of material what is most important and necessary, and, as rapidly as my words flow, clothe my thought in a form in which it can be grasped by the monster's intelligence, and may arouse its attention, and at the same time one must keep a sharp lookout that one's thoughts are conveyed, not just as they come, but in a certain order, essential for the correct composition of the picture I wish to sketch. Further, I endeavour to make my diction literary, my definitions brief and precise, my wording, as far as possible, simple and eloquent. Every minute I have to pull myself up and remember that I have only an hour and forty minutes at my disposal. In short, one has one's work cut out. At one and the same minute one has to play the part of savant and teacher and orator, and it's a bad thing if the orator gets the upper hand of the savant or of the teacher in one, or vice versa.
