Of all your ridiculous posts, this one is the most ridiculous. Congratulations.
Please explain. You don't even say which part of which post is "ridiculous".
If you are by any chance referring to this bit
. . . . . . . . . . .
In at least one case he (Rowbotham) actually makes the observation that the horizon is actually below eye-level at a higher elevation, then he dismisses it by showing he doesn't understand the purpose of a telescope on a theodolite.
Maybe you should read this before you say more?
From
Zetetic Astronomy, by 'Parallax' (pseud. Samuel Birley Rowbotham), TANGENTIAL HORIZON. Note that emphasis in the quote is mine.TANGENTIAL HORIZON.
IF a theodolite is placed on the sea shore, "levelled," and directed towards the sea, the line of the horizon will be a given amount below the cross-hair, and a certain "dip" or inclination from the level position will have to be made to bring the cross-hair and the sea-horizon together. If the theodolite is similarly fixed, but at a greater altitude, the space between the cross-hair and the sea horizon, and the dip of the instrument to bring them together, is also greater. From the above, which is perfectly true, it has been concluded that the surface of the earth is convex, and the line of sight over the sea tangential. As a proof that such is not the case, the following experiment may be tried:--
Place a theodolite on an eminence near the sea. "Level," and direct it over the water, when the horizon will be seen a little below the cross-hair or centre of the telescope, as shown in the diagram, fig. 30, page 41, and from the cause there assigned, viz., collimation, or refraction. Now let the instrument be inclined downwards until the cross-hair touches the horizon, as shown in fig. 31, page 41,
fig. 30, page 41 | | fig. 31, page 41 |
and in the following diagram, fig. 92. If the theodolite had a simple tube without lenses, instead of a telescope, which causes the appearance shown in , the
FIG. 92.
horizon would be seen in a line with the cross-hair, or axis of the eye, as at A, fig. 92, and the amount of "dip" required to bring the cross-hair and the horizon in contact with each other will be represented by the angle A, T, S, to which must be added the collimation. In every instance where the experiment has been specially tried, the dip without the collimation only amounted to the angle A, T, S; thus proving that the' surface of the sea, S, B, is horizontal, because parallel to the line A, T. If the water is convex, the line of sight, A, T, would be a tangent, and the dip to the horizon would be T, H, represented by the angle A, T, H. This angle, A, T, H, is never observed, but always A, T, S, plus collimation or divergence produced by the lenses in the telescope of the theodolite. Hence the surface of the waters is everywhere horizontal.
The words "collimation," "divergence," "refraction," &c., have many times been used in connection with this part of the subject, and the following very simple experiment will both exhibit what is meant, and show its influence in practice.
Take a "magnifying glass," or a convex lens, and hold it over a straight line drawn across a sheet of paper. If the line is drawn longer than the diameter of the lens, that part of it which is outside the lens will have a different position to that seen through it, as shown in the following diagram, fig. 93.
FIG. 93.
Instead of the line going uninterruptedly through the lens in the direction A, B, it will diverge, and appear at 1, 2; or it will appear above the line A, B, as at 3, 4, if the lens is held to the slightest amount above or below the actual centre.
A lens is a magnifying glass because it dilates, or spreads out from its centre, the objects seen through it. The infinitesimal or mathematical point actually in the centre is, of course, not visibly influenced, being in the very centre or on the true axis of the eye, but any part in the minutest degree out of that abstract centre is dilated, or diverged, or thrown further away from it than it would be to the naked eye; hence its apparent enlargement or expansion. Whatever, therefore, is magnified, is really so because thrown more or less out of the centre, and the more or less magnifying power of the lens is really the more or less divergence of the pencils of light on passing through the substance of which it is composed. In the telescope of a theodolite, or spirit-level, the spider's web of which the cross hair is made is placed in the actual centre; hence, in an observation, the point absolutely opposite to it is not seen, but only some other point minutely distant from it, but the distance of which is increased by the divergence caused by the lenses; and this divergence is what is called the "magnifying power." This is the source of those peculiarities which have been so very illogically considered to be proofs of the earth's rotundity. It is from this peculiarity that several gentlemen prematurely concluded that the water in the Bedford Canal was convex.
In all this Rowbotham clearly observes the "dip to the horizon", then tries to explain it away by claiming that
the magnification of the telescope is somehow distorting what we see, wheras all the magnification does is to make slight variations measurable.
These "dip angles to the horizon" will be very small for the heights he is likely to be referring to. He does not tell us the actual height he raised the theodolite to, but I doubt it would be over 100' or so. Now for an elevation of 100' the "dip angle to the horizon" is only about
11 minutes of arc (0.18°) and without magnification would hardly be visible.
Now, Rowbotham is so convinced of the Flat Earth, that he claims that the telescope's magnification is "causing an error".
But this "dip angle to the horizon" is real and I could post plenty of references where it is calculated and measured.
So, please tell me what bits of what posts are so ridiculous?