792 
vocacy in Hill’s writings. Terminology is 
largely flavored with words of Spanish origin, 
taken from the language that was once general 
and that is still familiar towards the Rio 
Grande. Plains are classified as constructional 
and destructional ; the first being the result of 
accumulation, the second of denudation. Con- 
structional plains are either sea-made or land- 
made ; the latter including many examples of 
surfaces covered by the coarse or fine wash from 
higher ground. The destructional plains here 
found are usually ‘stratum plains,’ that is, sur- 
faces of hard strata from which weaker overlying 
strata have been stripped; and of these three 
sub-classes are given, mesa plains, dip plains, 
and cut (or dissected) plains. Paleoplains is 
suggested as a name for buried destructional 
plains, but the word is objectionable etymologi- 
cally ; ancient plain may serve instead, as all 
the other classes of plains are indicated by ad- 
jectives. The descriptions of the Texan rivers 
show clearly enough that the conventional 
‘idea of a river as a constant current of water 
needs many modifications to fit it to regions of 
moderate rainfall and plentiful rock waste. 
THE NASHUA VALLEY, MASS. 
Tue ‘ Geological History of the Nashua Val- 
ley during the Tertiary and Quaternary periods’ 
is discussed by Crosby (Technology Quarterly, 
Boston, XII., 1899, 288-324, 2 maps, 2 pl.). The 
lower lands of eastern Massachusetts are re- 
garded as parts of a Tertiary peneplain, eroded 
beneath the uplifted Cretaceous peneplain of 
the central and western uplands of Massachu- 
setts ; the remnants of the latter form hills on 
the former. Previous to the Tertiary erosion, 
a coastal plain of Cretaceous sediments is sup- 
posed to have overlapped the southeastern part 
of the older peneplain and through this cover a 
number of east or southeast-flowing rivers were 
superposed on the greatly deformed and de- 
nuded underlying rocks, Traces of this system 
of drainage are found in the headwaters of cer- 
tain rivers whose valleys now converge in a 
general southeasterly direction towards notches 
in the hills through which their united volume 
is thought to have once continued in about the 
same course, but from which it seems to have 
been in several cases diverted by headwater 
SCIENCE. 
[N. S. Vou. XIII. No. 333. 
capture by small streams that grew along a belt 
of weak slates. The upper Nashua river is the 
best example of this kind, a number of its head- 
Rough Diagram of Nashua River System, Mass. 
Cities: Ay., Ayer; Cl., Clinton ; F., Fitchburg ; L., 
Lowell; N., Nashua. Streams: N. N., Upper 
Nashua ; Qt., Quinepoxet ; Sq., Squannacook ; St., 
Stillwater, Sy., Stony. Tertiary Water Gaps: A., 
Ayer ; C., Clinton ; Qd., Quinsigamond. 
water branches having been gathered from other 
systems into a single trunk. During the prog- 
ress of these captures and adjustments, broad, 
low-grade valleys were opened, their sub con- 
fluent floors constituting the Tertiary peneplain, 
above mentioned. A number of narrow gorges 
in these valley floors, now concealed by drift 
and discovered by borings in connection with 
the extensive works of the (Boston) Metropoli- 
tan Water Board, are explained as the result 
of a preglacial elevation ; and as such they may 
come to be compared with the narrow young 
valleys so distinctly seen in the uplifted Tertiary 
peneplain of Pennsylvania, but not hitherto 
identified in central New England. During the 
retreat of the ice sheet, lakes were formed in 
front of it in the upper Nashua valley; their 
outlets were across notches among the hills, at 
whose level a number of deltas and sandplains 
are now found. Drift obstructions in the broad 
notch traversed by the preglacial Nashua trunk 
seem to have diverted its flow northeastward 
along its present lower course into the Merri- 
mack. 
Itisto be hoped that fuller details, especially in 
