If I am looked upon as a person who wishes to give results to be used in faith by my pupils. It will be very easy to find many faults In this book. But I beg to say that I occupy a very different position. I aim, throughout, at showing a student how he, himself,. May attack problems which are, as yet, only partially solved, and if I give some of my own speculations, it is. Only when they are suggestive and likely to incite a student to go on with the. Study through experiment and calculation along lines which seem to me good ones.