Professor Wm. Romaine Newbold,
     212 St. Mark's Square,
       Philadelphia, Pa.

My dear Professor Newbold:

    I have been out of town part of the time since the receipt

of your letter of January 8.  Otherwise I should have replied to

it earlier.

    Here is a statement of the objection to your explanation.  You

are at liberty to use all or any part of it as you please.
    . . . . . . . . . . . . . . . . . . . . . . . . . . .
    "I understand that the manuscript gives a picture of a

celestial object with spiral arms and that the position of this

object, indicated in the manuscript, coincides with that of the

Andromeda nebula.  No telescope, even the best of modern ones,

will show this to the eye as a spiral structure.  Such a structure

is vaguely apparent on photographs and has been recognised as
                                      faint
spiral only because of the multitude of spiral
                                       ^
nebulae.

    "Your explanation of how it comes that Bacon was able to

draw the nebula as a spiral is that the nebula has turned over in

the six hundred and fifty intervening years, and is now seen nearly

edge on, whereas in Bacon's time, it was presented with no fore-

shortening.  If the nebula is distant three hundred light years

(and this is the very minimum allowable), then it can readily be

shown that the outer parts of the nebula must be travelling in

the line of sight at a rate of nearly one thousand kilometers

per second as compared with the axis of the nebula. If the dis-

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tance is one hundred times greater (and this is more likely), then

these relative velocities will be of the order of the speed of

light.

    Another objection is that your explanation would involve

rapid angular movements of some parts of the nebula across the

line of sight as compared with others, amounting in some portions

of the nebula to nearly ten seconds of arc a year.  If such a

change as this existed, it could easily be detected without measure-

ment, by merely comparing two photographs taken twenty or thirty

years apart.
    . . . . . . . . . . . . . . . . . . . . . . . . . . .
    It seems to me that the case for Roger Bacon's telescope would

have been much stronger without this drawing of the Andromeda neb-

ula than with it, for it surely offers great difficulties in the

way of an explanation; when we consider, as I have said above, that

the spiral character of this particular object was not rcognized

until about thirty years ago, and then only because of the dis-

covery of many excessively faint objects by means of photography.

    Many thanks for your references.  When I have the leisure I

intend to look up such of them as may be in our library,







W.