...while the individual man is an insoluble puzzle, in the aggregate he becomes a mathematical certainty.

There are heroisms all round us waiting to be done.

It has always seemed to me that so long as you produce your dramatic effect, accuracy of detail matters little. I have never striven for it and I have made some bad mistakes in consequence. What matter if I hold my readers?

Living, as I do, in an educated and scientific atmosphere, I could not have conceived that the first principles of zoology were so little known. Is it possible that you do not know the elementary fact in comparative anatomy, that the wing of a bird is really the forearm, while the wing of a bat consists of three elongated fingers with membranes between?

It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.

Crime is common. Logic is rare. Therefore it is upon the logic rather than upon the crime that you should dwell.

Even the best of us are thrown off some- times.