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 i