150 
NATURE 
[Fune 18, 1885 
debate, and are consequently infinitely freer to express 
our opinion and discuss the question from the one point 
of view of the interests of the projected reform. 
“The history of geography shows us very numerous 
attempts at the unification of longitudes, and on searching 
into the causes of the failure of those attempts, many of 
them very happily conceived, one is struck by the fact 
that they seem reducible to two main causes, one of a 
scientific, the other of a moral nature. The cause of a 
scientific nature lies in the inability of the ancients to 
determine exactly the relative positions of points taken 
on the globe, particularly in the case of an island re- 
moved from a continent, where the distance between the 
two was not determinable by itinerary measures. 
“Tt was thus, for example, that the first meridian of 
Marinus of Tyre and of Ptolemy, placed in the so-called 
Fortunate Islands, could not continue to be used, not- 
withstanding the advantage belonging to the choice of a 
position in the extreme west of the then known world, on 
account of the uncertainty attaching to this point of 
departure. 
“This very regrettable reverse served to give a wrong 
direction to the question. People were obliged to revert 
to the continent. Instead of regarding a common origin 
of longitudes indicated by nature, people took their first 
meridian from a capital, from remarkable places, from 
observations. The second cause to which I referred, 
the cause of a moral kind—namely, national jealousy— 
led to the multiplication of geographical origins, whereas 
the nature of things would have demanded their reduction 
to one single origin. 
“In the seventeenth century Cardinal de Richelieu, 
seeing this confusion, wanted to resume the idea of 
Marinus, and assembled at Paris learned men of France 
and foreign countries. The famous meridian of the 
island of Ferro was the result of their conferences. Here is 
a lesson which we ought not to lose sight of: the meridian of 
the island of Ferro, which had at first the purely geographi- 
cal and neutral character alone able to render it, and main- 
tain it as, a first international meridian, was displaced 
from its primary position by the geographer Guillaume 
Delisle, who, to simplify the figures, placed it in round 
numbers 20° west of Paris. This unhappy simplification 
completely changed the principle of impersonality. It 
was no longer an independent meridian, but the meridian 
of Paris disguised. Nor were the consequences slow in 
making themselves felt. The meridian of the island of 
Ferro, from that time regarded as a purely French 
meridian, wounded national susceptibilities, and thus lost 
the future which was certainly in store for it had it re- 
mained true to its first intention. 
“This was a real misfortune for geography. Our maps 
in their process of improvement ought to have main- 
tained the unity of departure, instead of confusing it ever 
more and more. 
“Tf from the time when astronomical methods were 
sufficiently advanced to allow the fixing of relative posi- 
tions with the degree of precision required for general 
geography (a state obtaining from the end of the seven- 
teenth century), the idea of Marinus of Tyre, so just 
and so geographical, had been resumed, the reform 
would have been effected two centuries sooner, and we 
should now have been in the full enjoyment of it. But 
people fell into the error of losing sight of the very prin- 
ciples of the question, an error to which the foundation 
and multiplication of observatories at that time greatly 
contributed. Furnishing relative positions, as they of 
course did, with great precision, each of these establish- 
ments was chosen by the nation possessing it to give it 
a point of departure for longitudes, so that the interven- 
tion of astronomy in these questions of a geographical 
nature—an intervention which, properly understood, should 
have been so advantageous—served only to remove us 
further from the object to be attained. 
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“The study of these questions leads us to establish 
a very necessary distinction between the meridians 
of a geographical or hydrographical nature, and the 
meridians of observatories. 
“The meridians of observatories must be regarded as 
essentially national. Their office is to enable observa- 
tories to depend on each other for the unification of their 
observations. They also serve as a basis for geodetic 
and topographical labours executed in connection with 
them. Their functions, however, being of an entirely 
special character, ought in general to be limited to the 
country possessing them. 
“ The first meridians in geography, on the other hand, 
do not require to be fixed with a precision quite so 
delicate as that exacted by astronomy; but in return 
their domain ought to be comprehensive, and while it is 
serviceable to multiply observatories, it is necessary to 
reduce to the utmost the origins of longitude in geo- 
graphy. 
“Tt may further be said that if the site of an observa- 
tory ought to be chosen under considerations of an 
astronomical description, a meridian of departure in 
geography ought to be fixed on grounds of a geographical 
description, 
“Have these two so different functions always been 
well comprehended, and a distinction of such vital 
moment properly observed? By no manner of means. 
“Seeing the observatories, by reason of the labours of 
high precision executed by them, furnish admirable data, 
each nation in a position to do so has assigned to its 
principal observatory not only the geodetic or topogra- 
phical works undertaken at home—a task very proper to 
it ; but likewise the general works of geography or hy- 
| drography executed abroad—a confusion of functions 
comprising in it the germs of all the difficulties under 
which we now labour. 
“Tn proportion, therefore, as cartographic labours ac- 
cumulated, the necessity of establishing unity in all that 
relates especially to general geography became more and 
more felt. This explains how the question of a single 
meridian of departure has been so often raised in recent 
times. 
“ Among the assemblies occupied with this question 
that principally deserving our attention is the one held at 
Rome last year. For many even of our colleagues the con- 
clusions adopted by the Congress of Rome settle the 
matter. Those conclusions must, therefore, very particu- 
larly engage our attention. 
“On reading the reports of the sittings of that assembly 
I was struck by the fact that in a meeting embracing so 
many men eminent for their learning and speculations, it 
was the U¢iditartan side of the question which was espe- 
cially considered, and which finally dictated the sense of 
the resolution taken. 
“Thus, instead of laying down the great principle that 
the meridian which should be offered to the world as a 
point of departure for all the longitudes of the earth 
ought, above everything else, to have an essentially geo- 
graphical and impersonal character, the question was 
simply asked, which among the meridians of observatories 
was the one possessing—permit me the expression—the 
largest following (éa clzentéle la plus nombreuse). 
“Tn a question of a geographical, much more than of 
a hydrographical, interest, as almost all mariners confess 
(seeing that, in fact, there exist but two prime hydrographi- 
cal meridians, Greenwich and Paris), a primary meridian 
is taken, the dominating character of which is marine. 
And this meridian, instead of being chosen according to: 
the configuration of the continents, is claimed for an ob- 
servatory. That is to say, the prime meridian is chosen for 
a mere chance spot on the globe, and one which, more- 
over, is very inconvenient, for the function the meridian 
is intended to perform. Instead, finally, of profiting by 
the lessons of the past, an element of national rivalry is 
eo 
