During the month of December, 1871, the appearance of a pamphlet by Mr. A. R. Wallace, "in reply to Mr. Hampden," was announced in several of the journals. Failing to obtain the production elsewhere, I inquired from the author "whence it could be obtained?" In a few days I was favoured with a copy, and, shortly afterwards, with the following letter:--

"Holly House, Barking, E.,
"January 6th, 1872.

     "Dear Sir,--May I beg you to state precisely what there is in the experiment exhibited by me on the Bedford Canal [[p. 57]] that is consistent with a plane earth and inconsistent with a globular one.

     "Of course you must allow that this is purely a matter of geometrical measurement, and can therefore only be decided by figures or diagrams accurately drawn. Also you must admit that the properties of the circle (as radically differing from those of the straight line) are exhibited on any scale or proportion,--that is, that a circle of an inch radius differs from a straight line in exactly the same way as a circle of a mile or of four thousand miles radius, only in a different degree. If you bear this in mind and show me by accurately drawn diagrams how you think my experiments are inconsistent with a spherical surface of the water or consistent a plane surface,--I think I can convince you of your error and show you how to make experiments in a room, that will demonstrate the error to any one really anxious to arrive at truth.

     "You may take the diagrams in Carpenter's "Water not Convex" as substantially correct.

"Yours very truly,
"ALFRED R. WALLACE."

     Owing to Mr. Wallace having abruptly quitted the above residence, without leaving behind him his future address, my subsequent letters were returned to me, but dilligent inquiries at length unabled me to resume the correspondence. [About this time Mr. Hampden had commenced to institute proceedings for the recovery of his £500, but no-one would insinuate, for a moment, that this was the cause of Mr. Wallace's exodus, any more than he would attribute the "journey" of discretionary French patriots, during the late Franco-German war, to the most distant sea-ports, to any fear, however remote, of the fortunes of war.] A desire I then, for obvious reasons, expressed, that the discussion should be public was considered in the following manner:--

"The Dell, Grays, Essex,
"May 22nd, 1872.

     "Dear Sir,--I offered to reply to any arguments you might adduce to prove that my Bedford Canal Experiments were consistent with a flat or inconsistent with a convex surface, and it matters not to me whether your communication be in writing or in print. You may also print my reply. But if you do so it must be clearly understood that you do not admit replies to me from such men as Hampden or Carpenter who are absolutely incapable of arguing the subject from want of the rudiments of mathematical knowledge, and from their constantly declining to test their assertions by experiment when asked to do so. I will however discuss the matter with you if you will agree to be guided by the demonstrations of geometry and to accept the test of experiment as to the accuracy of many of the assertions of "Parallax," Carpenter, and Hampden. But I will not enter into a discussion with all the incapable fools (educated or not) who would rush in and take a part in such a controversy.

     "I must also stipulate that your objections be separately and distinctly stated, and numbered consecutively; and, that whenever diagrams are required they must if possible be drawn accurately and to scale; also that you will make any simple experiments (such as can be made at home with little trouble and no expense) when we differ as to matters of fact that can be decided by such experiments; and lastly that you will state as to each point separately whether my replies are satisfactory or in what respect they are deficient.

     "These are the only conditions that at present occur to me and I think you will admit them to be fair and reasonable.

"I remain, Dear Sir,
"Yours very faithfully,
"ALFRED R. WALLACE."

"B. Chas. Brough, Esq."