"The study of Expression is difficult, owing to the movements being often extremely slight, and of a fleeting nature. A difference may be clearly perceived, and yet it may be impossible, at least I have found it so, to state in what the difference consists. When we witness any deep emotion, our sympathy is so strongly excited, that close obser vation is forgotten or rendered almost impossible; of which fact I have had many curious proofs. Our imagination is another and still more serious source ...