A typical letter handwritten by author in English and signed by author.
An original MS
Total Pages : 4
Pages with text: 4
Transcriber: Pearson, Keon
Transcription date: July 29, 2013
Scrutiny: 14/08/2013 - Catchpole, Caroline;
Signed off: no
The Dell, Grays. Essex.
April 20th. 1874
"Parallax", whose proper name is Rowbotham2, is not the man whose wager I have accepted - He is far too clever for that. Hampden3 was one of his dupes. Parallax makes the boldest false statements and as the number of those who can contradict him from actual experience is small his assertions are believed by thousands. As an example, in a recent correspondence with him he maintained that it is a property of the telescope to show distant objects depressed below objects less distant which are really in a line with them! This was [] to account for the admitted fact that in my experience the centre signal appeared 5 ft. above the distant one, although at the same height above the water. Thus:
[diagram of telescope and setup of water and object of telescope occurs here]
[diagram of distinct object seen in telescope at a distance of 6 miles occurs here]
This is appearance seen in the telescope, the lower disc in the middle signal 4 ft. below the top enabling the observer to estimate the amount of depression of the distant signal.
[diagram of telescope and objects, and the curved terrain in which they are implanted appears at the bottom of page 2]
[] The unprincipled character of the man is shown, by his admitting that in my case the middle signal appeared elevated, & calling in the aid of a supposed property of the telescope to account for it while in his lecture he maintains that it does not appear elevated!
As to the Ordnance Surveyors I have no doubt there is a rule that they are to make no allowance for curvature, -- because they are not allowed to take any but very short sights. The reason of the rule is obvious. If the surveyors were allowed to think that by making allowance for curvature long sights were as good as short ones, they would be liable to great errors, especially [] those arising from unequal refraction. I wonder at these lectures his gross false statements are not exposed; -- but I suppose there are always a majority present so ignorant as to believe that his assertions are as good as any one's.
The "Field" newspaper for March 26th. 18704 contains a full report of my experiments with diagrams, & for some weeks before & after there is are articles & correspondence on the subject.
I remain | Yours very truly | Alfred R. Wallace [signature]
T. W. Wallis Esq.
P.S. If you come to Grays I shall be happy to see you.5
1. Thomas Wilkinson Wallis (1821 - 1903) woodcarver
2. Parallax was a famous proponent of the theory that the earth is flat. His real name was Samuel Birley Rowbotham (1816 - 1884)
3. John Hampden (d. 1891) a flat-earther
4. The Field magazine was a sports magazine that published the results of ARW's Bedford Canal experiments, which demonstrated that the earth was indeed round.
5. This post script is written from the bottom to the top of the left side of the fourth page.
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