Aprit 19, 1901.] 
logical map might well serve as a guide to the 
observant traveler in this most picturesque dis- 
trict, 
REVERSION IN RIVER DEVELOPMENT. 
In the Seven-mountain district of Pennsylva- 
nia,'the anticlines and synclinesof the corrugated 
Medina sandstone, pitching gently eastward, 
form an extraordinary series of zigzag ridges. 
Streams rise in the apex of the synclinical reen- 
trants and flow eastward with the pitch of each 
synclinical axis toward the Susquehanna; and 
these axial streams receive branches that de- 
scend the dip-slope of the linear monoclinal 
ridges which diverge from each synclinal apex. 
Such a scheme of drainage has usually been 
called consequent ; yet when it is remembered 
that the present relief has been developed by 
the removal of a great series of strong and weak 
strata it appears that the existing streams are 
not the persistent successors of the original 
consequents, but that they have reverted to 
SCIENCE. 
629 
ancestral conditions after having passed through 
a systematic series of metamorphoses, as indi- 
cated in theaccompanying diagrams. The first 
section represents initial conditions. An orig- 
inal-cohsequent stream (A’) flows along the 
pitch of a synclinical axis of Pottsville con- 
glomerate and is fed by lateral consequents 
(L/A’) from the slopes of the enclosing anti- 
clines. Section 2 represents a later time when 
longitudinal subsequents have been developed 
along the anticlinal axes of the weak Mauch 
Chunk shales, thus shortening the laterals of 
the original system (Z/A’) by favoring the 
growth of obsequents (0’S’). In section 3 the 
new subsequents have shifted down the dip of 
their determining formation, thereby develop- 
ing a new lot of apparently consequent laterals 
(L/’S’), and the initial trough has been reversed 
into a narrow synclinal ridge, crowned by a 
remnant of Pottsville conglomerate. The orig- 
inal axial consequent (A4/) has vanished and an 
anticlinal subsequent of the second order (S/’) 
has appeared. With still further erosion, as per- 
mitted by successive uplifts, the two first-order 
longitudinal subsequents (S’, sect. 3) coalesce by 
continued monoclinal shifting, and thus form a 
new axial stream (A”, sect. 4) with appropriate 
laterals (L//A”’) in the trough of the Pocono 
syncline. By yet another series of analogous 
changes ending in the fifth section, a third-order 
axial stream will be developed (A’”) fed by a 
series of third-order laterals (L///A’””) on the 
Medina syncline, such as at present exist. Al- 
though these streams closely imitate the ances- 
tral consequents of the first section (A’,L’A’), 
it is evident that the imitation is due to rever- 
sion and not to the persistence of a fixed type. 
Streams of this kind might be called reversional - 
consequents, renewed consequents, reconse- 
quents, or simply resequents. 
W. M. Davis, 
CURRENT NOTES ON METEOROLOGY. 
QUARTERLY JOURNAL OF THE ROYAL METEORO- 
LOGICAL SOCIETY. 
THE January Quarterly Journal of the Royal 
Meteorological Society contains several articles of 
general interest. Dr. Nils Ekholm contributes 
a paper ‘On the Variations of the Climate of 
the Geological and Historical Past and their 
