Professor ADAMS, thinks that I overlook too much the practical side of
the question; namely, how a prime meridian can be established so as to
cause the least inconvenience. He says that I pay too much attention
to what he calls a question of sentiment, and he concludes by
expressing the hope that all nations will lay aside their national
pride and only be guided by this consideration: What meridian offers
the greatest practical advantages? My reply is that I intend no more
than Professor ADAMS to place the question upon the ground of national
pride; but it is one thing to speak in the name of national pride and
another to foresee that this sentiment common to all men, may show
itself, and that we should avoid conclusions likely to arouse it, or
we may compromise our success. That is all our argument; and the
history of the great nation to which Professor ADAMS belongs furnishes
us with examples of considerable significance, for the French meridian
of Ferro was never adopted by the English, notwithstanding its happy
geographical situation, and we all still awaiting the honor of seeing
the adoption of the metrical system for common use in England.
But let us put aside these questions which I would not have been the
first to touch upon, and place ourselves upon the true ground of the
importance of the proposed reform, which is the only one worthy of
ourselves or of this discussion. We do not refuse to enter into an
agreement on account of a mere question, of national pride, and the
statement of the changes and expenses to which we should have to
submit in order to accomplish the agreement is a sufficient proof of
this.
But we consider that a reform which consists in giving to a
geographical question one of the worst solutions possible, simply on
the ground of practical convenience, that is to say, the advantage to
yourselves and those you represent, of having nothing to change,
either in your maps, customs, or traditions--such a solution, I say,
can have no future before it, and we refuse to take part in it.
Prof. ABBE, Delegate of the United States, stated that the Delegate of
France, Mr. JANSSEN, had made a very important proposition to the
Conference: That the meridian adopted should be a neutral one. He said
that he had endeavored to determine what a neutral meridian is. On
what principle shall the Conference fix upon a neutral meridian, and
what is a neutral meridian? Shall it be historical, geographical,
scientific, or arithmetical? In what way shall it be fixed upon? He
looked back a little into the history of an important system adopted
some years ago. France determined to give us a neutral system of
weights and measures, and the world now thanks her for it. She
determined that the base of this neutral system should be the
ten-millionth part of a quadrant of the meridian. She fixed it by
measurement, and to-day we use the metre as the standard in all
important scientific work; but is that metre part of a neutral
system? Is our metric system neutral? It was intended to be, but it is
not; we are using a French system. Had the English, or the Germans, or
the Americans taken the ten-millionth part of the quadrant of the
meridian, they would have arrived at a slightly different measure, and
there would have been an English, a German, and an American measure.
We are using the French metric system. It was intended to be a neutral
system, but it is a French system. We adopt it because it deserves our
admiration, but it is not a neutral system. The various nations of the
world might meet and agree upon some slight modification of this
metric system which would agree with the results of all scientific
investigations, and thus make it international instead of French; but
we do not care to do that, and are willing to adopt one system, taking
the standard of Paris as our standard. How shall we determine a
neutral system of longitude? The expression "neutral system of
longitude" is a myth, a fancy, a piece of poetry, unless you can tell
precisely how to do it. He would vote for a neutral system if the
French representatives can tell the Conference clearly how to decide
that it is neutral, and satisfy them that it is not national in any
way.
Mr. JANSSEN, Delegate of France, said:
I perfectly understand the objection of my honorable colleague, Prof.
ABBE. He asks what is a neutral meridian, and adds that the metre
itself does not appear to him to be a neutral measure, but to be a
French measure. He relies upon the consideration that if the English,
the Americans, and Germans, in adopting a definition of the metre, had
measured it for themselves, they would have arrived each at a slightly
different result, which would have given us an English, American, and
German metre; nevertheless, he adds, we use the French metre, because
we find it so admirable.
I would answer, first, that the metre, as far as the measure is
derived from the dimensions of the earth, is not French, and it was
precisely to take away this character of nationality that those who
fixed on the metre sought to establish it on the dimensions of the
earth itself. What is French is the particular metre of our national
archives, which exhibits a very slight difference from that which our
actual geodesy would have given us. Also, I think that if, at the time
of the adoption of the Convention du Mêtre, in which the nations of
Europe participated, we had slightly changed the length of our
standard to make it agree with the result of actual geodetic
measurements, we should have done an excellent thing in depriving this
measure of any shadow of nationality. I agree with my honorable
colleague that if a few slight changes adopted by common accord could
perfect the metrical system, we French ought to have no motive for
opposing it. We have the honor of having invented a system of measures
which, being based upon considerations of a purely scientific nature,
has been accepted by all. Therefore if it can be said with truth that
the metre of the Archives of Paris is French, (not intentionally, but
because it bears the mark of an error of French origin,) it is an
international metre, by the same title that the discovery of the
satellites of Mars made by my friend, Prof. Asaph Hall, whom I have
the pleasure of seeing here, is scientific and of a universal nature.
The metre--equal to the ten-millionth part of the distance from the
equator to the pole--is no more French than that distance itself, and,
nevertheless, if the Americans, English, or Germans had measured it,
they would each have arrived at a slightly different metre.
Now, my honorable colleague adds that a neutral meridian appears to
him a myth, a fancy, a piece of poetry, so long as we have not exactly
settled the method of determining it. I shall disregard the
expressions which my honorable colleague has thus introduced into the
discussion, because this discussion should be serious. It is plain
that Prof. ABBE did not thoroughly apprehend the explanations which I
gave of the proper methods of fixing the initial meridian, and of the
conditions which make a meridian neutral; but I return to them, since
I am invited to do so. Our meridian will be neutral if, in place of
taking one of those which are fixed by the existing great
observatories, to which, consequently, the name of a nation is
attached, and which by long usage is identified with that nation, we
choose a meridian based only upon geographical considerations, and
upon the uses for which we propose to adopt it.
Do you want a striking example of what differentiates a neutral
meridian from a national meridian? In order to avoid the confusion
which existed in geography at the beginning of the seventeenth
century, on account of the multiplicity of initial meridians then in
use, a congress of learned men, assembled in Paris at the instance of
Richelieu to select a new common meridian, fixed its choice on the
most eastern point of the Island of Ferro. This was a purely
geographical meridian, being attached to no capital, to no national
observatory, and consequently neutral, or, if you please, purely
geographical. Later, Le père Feuillet, sent in 1724 by the Academy of
Sciences to determine the exact longitude of the initial point, having
given the figure 19° 55' 3" west of Paris, the geographer, Delisle,
for the sake of simplicity, adopted the round number 20°; and, as I
stated a little while ago, this alteration completely changed the
character of this prime meridian. It ceased to be neutral, and became
merely the meridian of Paris disguised, as has been truly said, and
the English, notably, never adopted it. Here is the difference,
gentlemen, between a neutral meridian and a national meridian.
And, parenthetically, you see, gentlemen, how dangerous it is to
awaken national susceptibilities on a subject of a purely scientific
nature. Now allow me to add that, if in 1633 it was possible to find a
neutral meridian, a purely geographical meridian, an independent
meridian, it may easily be done in 1884 if we wish to do so; and that
a point chosen on purely geographical considerations, either in
Behring's Strait or in the Azores, could be much better determined now
than was possible to Father Feuillet in 1724, and could take the
position which the meridian of Ferro would not have lost had it not
been confounded with the meridian of Paris.
Professor J. C. ADAMS, Delegate of Great Britain, stated that he
merely desired to refer to one subject touched on by the Delegate of
France, Mr. JANSSEN, whose opinion he thought could hardly be
supported, and that was that the question of longitude was purely one
of geography. He desired to controvert that, and to hold that the
question of longitude was purely one of astronomical observation. The
difference of longitude between two places could not be determined by
geodetic observations, because to do this you must take hypothesis as
to the figure of the earth, and the figure of the earth is not a
simple figure. You may take as hypothesis that the figure of the earth
is spheroidal, and that the ratio of the axes is exactly defined. Now,
in the first place, we are not agreed as to the exact ratio of the
axes, nor are we agreed as to the exact figure of the earth. If an
attempt is made to measure the difference of longitude between two
points on the earth's surface, especially when they are a considerable
distance from each other, it is necessary to depend upon astronomical
observations. In attempting to deduce the difference of longitude from
geodetic measures, you must assume that the true figure and dimensions
of the earth are known, which is far from being the case. The theory
that the prime meridian is a matter purely of a geographical nature is
liable to the fatal objection that the determination of the difference
of longitude between one place and the other is really the
determination of the difference of time of the passage of a star
across the meridian of the two places concerned. That is very
definite. You observe the transit of the star at one place, and you
observe the transit of the star at the other place, and by means of
telegraphic communications you are able to determine their difference
of longitude independent of the figure of the earth. He said, in
conclusion, that he thought the honorable Delegate of France was
mistaken upon the main point which he had just referred to, if,
indeed, he had rightly understood him.
M. JANSSEN, Delegate of France, replied as follows:
I think that M. ADAMS entirely misunderstands me. I agree with him
absolutely in thinking that longitudes cannot be determined,
especially of places far apart, except by astronomical methods.
Geodesy can only furnish it for short distances; in such cases, it is
true, it supplies it with a degree of accuracy which meridianal
observations cannot attain. So, if the question be to determine
rigorously the difference of longitude in time between two places on
the earth at considerable distances apart, it becomes one of
astronomy, because here it is astronomy which gives the quickest and
most accurate solution. For these reasons if, for instance, we should
wish to connect a given observatory with a point situated on the other
side of the ocean which had been chosen as the starting point of
longitudes, it would become a question of astronomy. Astronomy here is
an admirable instrument for the solution, but it should only be the
instrument.
On the contrary, the question becomes geographical, if it be that of
determining where it will be most convenient to fix the origin of
terrestrial longitudes. If the question be, for instance, to select
one or another point, in some one or other ocean, astronomy has
nothing to do with it, and when it wishes to impose upon us one of its
observatories to fulfil such a function it tends to give an inaccurate
solution.
At first sight it may seem that any point might become a starting
point for terrestial longitudes, but when we study the question a
little more we see there may be great advantages in choosing some one
point in preference to some other. Hence it is that all geographers
have agreed to place initial meridians, when possible, in the oceans.
The PRESIDENT stated that, in accordance with the decision of the
Conference, he had sent to the scientists named by them invitations to
a seat upon this floor. The Chair sees several of these gentlemen here
to-day, notably one of the most eminent astronomers of this country,
to whom his countrymen are always ready to do homage, Professor
Newcomb, Superintendent of the United States Nautical Almanac. If it
be the pleasure of the Congress, the Chair will now request Professor
Newcomb to give us his views upon the resolution now under discussion.
No objection being made to the proposition of the President, Professor
NEWCOMB arose and said:
That in reference to the remarks of the distinguished Delegate of
France, Professor JANSSEN, he would prefer, if the Conference would
consent, to study his arguments more carefully when they should be in
print.
He remarked that some points raised by that argument have been already
replied to, and he wished now more particularly to request that
Professor JANSSEN would define precisely what he meant by "a neutral
meridian;" that he had partially answered this question in reply to
Professor ABEÉ; but that there was a more fundamental point, one of
practice, which must be brought in and kept in mind at every step, and
which was raised by Commander SAMPSON'S paper, to which he had
listened with great interest. Commander SAMPSON held that it would be
necessary to have a fixed observatory on the chosen prime meridian,
but he (Professor NEWCOMB) did not concur in that view, but rather
agreed to a limited extent with what Professor JANSSEN had said on
that question.
In choosing a meridian from which to count longitude, you meet a
difficult problem. You have a point on the globe defined as the first
meridian. This would be taken as the initial point of departure, and
you are to determine the longitude of a certain place from that point.
Now, doubtless, there is no other way to do this than to have an
astronomical instrument and telegraphic communication. And if they
chose the Azores or Behring's Strait, in neither case could they mount
a transit instrument or have a system of telegraphic communication.
Nor could we make a determination of longitude from a single fixed
observatory in any case.
He then stated that it was impracticable under any circumstances to
have an absolutely neutral prime meridian; that the definition of the
prime meridian must practically depend upon subsidiary considerations,
no matter where it might be located. In the practical work of
determining longitudes a connection with the prime meridian cannot be
made in each case. What is really determined is the longitude from
some intermediate point, generally in the same country, and in
telegraphic communication with the place whose longitude we wish to
know. This intermediate point would, for the time, be the practical
prime meridian. But the longitude of this point itself must always be
uncertain. Science is continually advancing in accuracy, and we find
that we continually need to correct the longitude of our intermediate
meridian, and hence of all points determined from it. How can this
difficulty of constantly changing longitudes be avoided? He replied
that each system of connected longitudes must rest upon its own basis.
It must be referred to an assumed prime meridian, and the
measurements must be made from that, even if it be found to be
somewhat in error. If some such system had been adopted thirty or
forty years ago, we would have avoided the confusion arising from the
fact that the longitudes given on many maps do not refer at all to any
absolute meridian. All that is known is that the astronomers
determined the longitude of the place, and then the maps had to be
corrected accordingly. The longitude of one place would be determined
from Cambridge, and perhaps in the neighborhood is another place
determined from the observatory at Washington. In either case we know
nothing of the longitude of Cambridge or Washington which the observer
assumed in his calculations.
Generally, in determining longitude, the country adopts the principal
place within its confines as a subsidiary prime meridian, and the
assumed longitude of this place is necessarily selected somewhat
arbitrarily. The longitude, for instance, of Washington was, thirty
years ago, known to be nearly 5 hours 8 minutes and 12 seconds west
from Greenwich. Had we adopted this difference by law, it would have
amounted to choosing for our prime meridian a point 5 hours 8 minutes
and 12 seconds east of Washington, whether we happened to strike the
transit instrument at Greenwich or not. This would have fixed an
assumed longitude for the Cambridge observatory and for all points
within our telegraphic net-work. We should have had a practical
system, which might, however, require to be corrected from time to
time, if some slight error were found in the assumed longitude of
Washington.
In the present state of astronomical observation these little errors
are of no consequence except in some very refined astronomical
discussions. For all geographical and perhaps geodetical purposes the
error may be regarded as zero, and it may be said, in regard to
astronomical work, that it will always be independent of any meridian
that might be chosen.
But even if this difficulty were avoided, he could not see how they
could have any place which would come within the definition of a
neutral meridian. Supposing they took the Azores, they belong to
Portugal; then certainly they would have a Portuguese prime meridian,
belonging to the Portuguese nation. Thus they would no longer have a
neutral point, if he (Professor NEWCOMB) rightly understood the
meaning of Professor JANSSEN.
He said that the Delegate of Great Britain, Professor ADAMS, had
expressed very clearly his (Professor NEWCOMB'S) ideas, and the
difficulty we have in meeting the propositions of the French
Delegates; that what he had said would apply very properly to any
neutral meridian that might be chosen in accordance with the plans of
Professor JANSSEN. Whatever that meridian might be, we must always
assume for it a certain number of degrees from the capital of the
country, where the place to be determined is located, and then take
that imaginary meridian instead of a real point on the surface of the
globe.
It is true that this is perfectly practicable, and on that theory
there might not be any necessity of having an astronomical
observatory. But why we should go to this trouble and expense Mr.
JANSSEN did not make very clear; his considerations were purely
sentimental, as was remarked by the Delegate of Great Britain,
Professor ADAMS, and he (Prof. NEWCOMB) did not see what advantage
would be gained by a neutral meridian in preference to one fixed by
convenience.
In order that a discussion may proceed, it is necessary to agree on a
given basis from which to start, and it is extremely difficult to
agree upon a basis if there are considerations of sentiment
introduced, because such considerations are peculiar to each person.
He therefore wished to propose this question again to the Delegate of
France, namely, what advantages can we derive from fixing upon a
neutral meridian?
Mr. JANSSEN, Delegate of France, said:
Professor NEWCOMB asks me to point out the advantages of a neutral
meridian. These advantages are of two kinds--they are of a
geographical nature and a moral nature. Let us examine the first. By
placing the initial meridian between Asia and America, we get away
from the centres of population, which is almost indispensable in view
of the change of dates. We divide the world into two parts, the Old
World and the New. The advantage of drawing the prime meridian
through the ocean has always been understood, and it was precisely for
this reason that Marinus of Tyre, during the first century, placed it
at the Fortunate Isles, west of the African Continent. It is idle to
urge the difficulty of fixing such a meridian as an objection.
Astronomy is so far advanced in our day as to enable us to make this
calculation with all desirable accuracy.
As to the methods of obtaining this meridian exactly, there are
several. I have already spoken of them, but I return to the subject,
since more details are desired. These methods fall under two principal
heads. We can, and that is the ancient idea, choose some remarkable
physical point--as, for instance, the extremity of an island, a
strait, the summit of a mountain--and determine approximately the
distance in longitude of this point from the points of reference,
which are at present the observatories. This method, if all the
precision that science can now attain is required, would be costly in
certain cases. For the Azores the expense would be small, because of
the proximity of the telegraphic cables; it would be much greater for
Behring Straits. On the hypothesis of the employment of this method,
it would evidently be necessary to place our meridian at the Azores.
According to the other method, it is not the physical point which is
fixed, but simply the distance of the assumed origin from the points
of comparison. For example, admit that the general definition of our
prime meridian was that it should pass through the middle of Behring
Straits. To obtain its theoretical definition, we should obtain a
position of this point, either by summary observations of the nature
of hydrographic surveys, or by the aid of existing information, and
the longitude thus obtained would be connected with the observatories
best connected with each other. A list of the differences of longitude
would become the definition of our meridian, and not the physical
point in the sea which marks the exact middle of the strait. If, now,
we absolutely wished for a physical point, we have the Island of St.
Lawrence, which is cut towards its eastern part by such a meridian,
and we could put a point of reference there, subject to the condition
that the position of this point should conform to the definition, and
that it should be removed, in one direction or the other, until it did
conform to it. As to the very slight errors which might still affect
the relative positions of the great observatories actually connected
by electricity, they do not concern geography. If I am not mistaken,
the eminent Superintendent of the American Nautical Almanac
acknowledges that we could thus avoid the difficulties which might
result from the changes to which the perfecting of science would in
the course of time give rise in the statement of longitudes.
In this manner the expense would be nothing or small. Thus, also, the
meridian would be truly neutral, both by reason of its position in the
ocean between the continents, and by reason of its definition, since
the zero of longitude would then be so placed as to occupy a point not
identified with any nation. This illustration appears to me to answer
the demands of Professor NEWCOMB. I have taken it only for that
reason, for I maintain no particular method, but only the principle of
neutrality.