SCIENCE 
NEW YORK, JANUARY 5, 1894. 
RIVER COURSES IN THE JURA MOUNTAINS. 
BY EMM. DE MARGERIE, PARIS, FRANCE, 
Ir is well known to readers of Science that Prof. W. 
M. Davis, in his admirable analysis of the origin of the 
Valleys of Pennsylvania (National Geogr. Mag., Vol. L., 
No. 3, 1889), started from the assumption of a purely 
consequent, original course for the rivers which have 
excavated most of the Appalachian Valleys. As an 
illustration of such a kind of drainage system existing 
at the present time the Jura Mountains were given, fol- 
lowing a statement published by Col. de la Noé and 
myself in our joint work, ‘‘Les Formes du Terrain” 
(Paris, 1888). 
More recently, however, Prof. Davis has been led to 
change this view, according to the results reached by 
Mr. Aug. F. Foerste, in his valuable account of ‘‘The 
Drainage of the Bernese Jura” (Proc. Boston Soc. Nat. 
Hist., Vol. XXV., p. 392-420, 1892). 
While admitting that Mr. Foerste has clearly shown 
that the River Birse could not have taken its present 
path if it had been a purely original consequent stream, 
I cannot agree with him when he endeavors to show 
that recourse must, of necessity, be had to the postulate 
of an antecedent origin; for it seems highly improbable 
that such a small river, whose upper drainage area is of 
so little extent, could have victoriously reinted the up- 
lift of such great anticlinals as the Graitery, the 
Raimeux, the Roche and the Choindez folds are. The 
failure of other explanations to meet the facts, which is 
given by Mr. Foerste, together with the systematic ar- 
rangement of several series of cluses in straight lines, as 
the main support of the theory of an antecedent origin 
(loc. cit., p. 411), does not seem to constitute a valid 
argument: are we absolutely certain not to have over- 
looked some possibility, which could turn out, when fol- 
lowed out in detail, to involve the true explanation ? 
But, apart from these considerations, if such is really 
the origin of the Cirques followed by the Birse, we 
should expect to find in the Jura Mountains many cther 
examples of the same absence of relation between river- 
courses and constructional form. In order to test ina 
definite manner the validity of Mr. Foerste’s conclu- 
sions, and to see whether his theory may be of general 
application in the Jura or not, my friend, Col. de la 
Noé, has lately drawn, at my request, a large map of 
the whole country between Bale, on the Rhine, and 
Belley, near the Rhone, a map upon which all the 
heights have been referred to a common datum plane 
(in a stratigraphical sense), viz.: the limit between the 
uppermost Jurassic beds and the base of the Cretaceous 
(Neocomien); as a basis for the work, use was made of 
the sheets of the new map of France, drawn in contours 
with 20 metres .vertical interval, on the scale of 
Xe Gl 5 Dei TJ ih , i .- del dal . peal t J. 
_1:200,000, geological boundaries being adjusted on the 
Same from, the detailed, maps of the French and Swiss 
Surveys. The altitude reached at any point’ by the 
horizon selected, above the present surface, if denuded, 
or underground, if covered by more recent deposits, 
could be computed with a fair degree of approximation, 
thanks to the numerous measurements of sections pub- 
lished during the last decade for various parts of 
the Jura; contours were then constructed, every roo 
metres apart, without any regard to the present topog- 
raphy, and a photographic proof of the map, reduced 
one-half, colored in the manner of an ordinary hypso- 
metric map.’ 
The result is very striking: nearly everywhere a 
strict accordance is shown to exist between the actual 
courses of rivers and the distribution of the lowest parts 
of the constructional surface; the larger streams, those 
which might be expected to exhibit the most irregular 
courses if the assumption of an antecedent origin was 
correct, are precisely those which follow the most close- 
ly synclinal depressions, making use here and there of 
cols where anticlinal arches are locally lowered in a 
transverse direction. Such is the case for the river 
Ain, the longest among the tributaries which the Rhone 
receives from the Jura, and for the Doubs, the longest 
stream in the whole region. A beautiful illustration of 
a series of cluses arranged in a straight line, and demon- 
strably correlated with the lowering of several adjacent 
anticlines from both sides, is given by the river Bienne, 
between the town of St. Claude and its junction with 
the Ain. Many other cases might be pointed out to 
the same effect, viz.: that the Jura drainage, as a 
whole, is typically consequent upon the deformations, 
and that, accordingly, Professor Davis was quite right in 
postulating as the initial stage, in the development of 
Pennsylvania rivers, essentially original courses during 
Permian time. ; : 
“As to the special case of the Birse, no doubt that ap- 
parent exception remains to be explained; that back- 
ward erosion may have been concerned in the produc- 
tion of the Bernese Cirques, Mr. Foerste himself seems 
to concede, in alluding to the Crémine cirque; and I 
believe nobody can have seen the Soulce depression, on 
the outside of the Choindez fold, or the great ravine 
south of Chatillon, a little more to the east, without be- 
ing struck by the analogy of both features with an un- 
perfected cluse—and their purely regressive origin is 
beyond question. 
A last word about the crystalline pebbles in the Ter- 
tiaries of the Bernese Jura: Mr. Foerste, following J. 
B. Greppin, believes that they came from the Schwartz- 
wald, to the north of the district. But that conclu- 
sion is far from certain. Dr. Rollier, who has care- 
fully surveyed the district on the scale of 1:25,000, 
1The method here described does not seem to have been, as yet, appreci- 
ated to its full value. Originated, I believe, in America, with Professor 
Lesley’s efforts, and splendidly applied to the study of the anthracite fields 
of Pennsylvania by his lamented assistant, the late Charles A. Ashburner, 
it has been but little resorted to, outside of very limited districts and for 
purely scientific purposes. So far as I am aware, the only similar attempts 
yet made to construct in contour-lines stereograms of displacements, for a 
broad geographical area, are Mr. Dollius’s “Carte hypsometrique de la Sur- 
face de la Craie dans le Bassin de Paris,”’ on the scale of 1:1,000,000, published 
in Bulletin No. 14 of the French Geological Survey (Paris, 1890), and the two 
maps illustrating the shape of the Trenton limestone in Ohio and Indiana, 
published by Professor Orton and Mr. Phinney in'the Eighth and Eleventh 
Annual Reportsjof, the United),Statés Geological Survey, respectivdlyi!) 1 
myself constructed, several years ago, a contour map, still unpublished, 
showing the deformations, of the Dakota. sandstone in, western Colorado 
(from Hayden's atlas of that state), and where the same agreement between 
“structure and hydrography as is here advocated for the Jura was plainly ex- 
- hibited. The construction of Such maps would be specially fitting in those 
countries where detailed geological surveys are conducted upon topograph- 
ical maps in contours as a basis, such as are in most parts of Germany. 
