Dear Mrs. Fisher,—­Thanks for your letter.  Am sorry I have not converted you, but perhaps it will come yet!  I will only make one remark as to your conclusion.

I have not attempted to prove a negative!  That is not necessary.  What I claim to have done is, to have shown that all the evidence we have, be it much or little, is decidedly against not only other solar planets having inhabitants, but also, as far as probabilities are concerned, equally against it in any supposed stellar planets—­for not one has been proved to exist.  There is absolutely no evidence which shows even a probability of there being other inhabited worlds.  It is all pure speculation, depending upon our ideas as to what the universe is for, as to what we think (some of us!) ought to be!  That is not evidence, even of the flimsiest.  All I maintain is that mine is evidence, founded on physical probabilities, and that, as against no evidence at all—­no proved physical probability—­mine holds the field!—­Yours very truly,

ALFRED R. WALLACE.

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TO MR. E. SMEDLEY

Broadstone, Dorset.  July 24, 1907.

Dear Mr. Smedley,—­ ...  I write chiefly to tell you that I have read Mr. Lowell’s last book, “Mars and its Canals,” and am now writing an article, or perhaps a small book, about it.  I am sure his theories are all wrong, and I am showing why, so that anyone can see his fallacies.  His observations, drawings, photographs, etc., are all quite right, and I believe true to nature, but his interpretation of what he sees is wrong—­often even to absurdity.  He began by thinking the straight lines are works of art, and as he finds more and more of these straight lines, he thinks that proves more completely that they are works of art, and then he twists all other evidence to suit that.  The book is not very well written, but no doubt the newspaper men think that as he is such a great astronomer he must know what it all means!

I am more than ever convinced that Mars is totally uninhabitable....—­Yours very truly,

ALFRED R. WALLACE.

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TO PROF.  BARRETT

Broadstone, Wimborne.  August 10, 1907.

My dear Barrett,—­Thanks for your letter, and your friend Prof.  Stroud’s.  I have come to the sad conclusion that it is hopeless to get any mathematician to trouble himself to track out Lowell’s obscurities and fallacies....  So, being driven on to my own resources, I have worked out a mode of estimating (within limits) the temperature of Mars, without any mathematical formulae—­and only a little arithmetic.  I want to know if there is any fallacy in it, and therefore take the liberty of sending it to you, as you are taking your holiday, just to read it over and tell me if you see any flaw in it.  I also send my short summary of Lowell’s Philosophical Magazine paper, so that you can see if my criticism at the end is fair, and whether his words really mean what to me they seem to....—­Yours very sincerely,