Dear Sir

I am sorry to say that it is impossible for me give you the least aid, as I have never attended to any mechanical subjects.—¹ I sh^d. doubt whether it would be possible to train birds to fly in a certain direction in a body, though I am aware that they have been taught some tricks— Their mental powers are probably much below those of mammals.—

It is said, & I suppose truly, that an Eagle will carry a lamb, this shows that a bird may have great power for a short distance.—

I cannot remember your essay with sufficient distinctness to make any remarks on it.² When a man is old & works hard, one subject drives others out of his head.—

I hope to read what you say about M^r. Bradlaugh.³

I remain | Dear Sir | Yours faithfully. | Ch. Darwin.