252 The Ajnerican Geologist. April, 1900 
of the various theories that have been abvanced in this field, rather than 
to propound new views. 
Professor Tarr ascribes chief potency to glacial erosion among the 
causes of the lake basins. He thinks, with Gilbert, that the instability 
of that part of the earth's crust, not yet at rest from its disturbances by 
the load of the ice-sheet and by its removal, may possibly result in di- 
version of the drainage from the lakes above Ontario to the Mississippi 
by way of the old Chicago outlet. Concerning the duration of Niagara 
and of Postglacial time, he thinks it probably less than 10,000 years, 
though more definite knowledge of the Nipissing outlet from lake Hu- 
ron eastward is desired. w. u. 
Geological History of the Nashua Valley during the Tertiary and 
Quaternary Periods. By W. O. Crosby. Technology Quarterly, vol. 
XII, pp. 288-324, with two maps and two plates of scenery from photo- 
graphs; December, 1899. 
Eastern Massachusetts and southern New Hampshire present two 
ancient peneplains, one of Cretaceous and the other of Tertiary age, 
each moderately hilly. The latter, adjoining the coast and reaching 
many miles inland, rises to a normal elevation of 100 to 200 feet. The 
valley of the Nashua river, eroded below the Cretaceous peneplain in a 
belt of relatively soft argillaceous strata, is regarded as continuous sea- 
ward with the Tertiary peneplain. Buried gorges in the Nashua valley, 
filled and covered with the glacial and modified drift, are revealed by 
wells and by borings on the site of the Wachusett dam, near Clinton, 
Mass., which has been built across the Nashua valley to form a large 
reservoir supplementing the water supply of Boston and its suburbs. 
Long stability of the land during Tertiary time appears to have been, 
terminated by an important pre-glacial uplift, when the gorges were cut, 
ending probably in the accumulation of the ice-sheet. 
At the end of the Glacial period, the recession of the border of the 
ice-sheet is thought to have been here from southwest to northeast; and 
in the Nashua valley, declining northeasterly, a glacial lake of very ir- 
regular outlines was formed, attaining, in the combined area of all its 
stages, a length of about twenty-five miles, with a maximum width of 
about seven miles. It had successive outlets, each lower than the pre- 
ceeding, uncovered by the retreat of the ice border. Like the similar 
glacial lake of the Contoocook river valley in New Hampshire, the re- 
cord of lake Nashua consists chiefly in its delta deposits and its tracts 
of modified drift spread at the old lake levels. w. u. 
MONTHLY AUTHORS' CATALOGUE 
OF American Geological Literature, 
Arranged Alphabetically.* 
Barbour, E. H. 
Wells and windmills of Nebraska. (Water Sup. and Irri. papers of 
the U. S. G. S., No. 29. Washington. 1899.) 
*Tliis list includes titles of articles received up to the 2i)»^h of the preceding 
month, including general geology, physiography, paleontology, petrology and 
mineralogy. 
