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