Geology. 287 



ination of the structural features and glacial deposits of the Dan- 

 bury region, has demonstrated that ' ' the lower Housatonic has 

 always maintained its course diagonal to the strike of formations 

 and that differential erosion which reaches its maximum expres- 

 sion in limestone areas is responsible for the impression that the 

 Still River lowland and other valleys west of the Housatonic may 

 once have been occupied by the later stream" — a conclusion 

 opposed to the views of Hobbs (Bull. Geol. Soc. Am., vol. 13, pp. 

 17-26, 1901) and of Crosby (Tech. Quart., vol. 13, p. 120, 1900). 

 The paper by Dr. Harvey has much more than local interest for 

 the physiographic history of the region which includes the Housa- 

 tonic, the Croton, and the Saugatuck drainage systems involves 

 the interpretation of the topographic features of southern New 

 England. 



Bulletin 31. A Check-List of Connecticut Insects; by W. E. 

 Britton. 397 pp., 1920. The collections of Connecticut insects 

 at the Connecticut Agricultural Experiment Station are the most 

 important in existence. Dr. W. E. Britton has listed these col- 

 lections in systematic order, following a plan which will make 

 this bulletin an indispensable handbook for professional entomol- 

 ogists and for amateurs interested in the insect life of their home 

 region. The list includes 6,781 species and varieties grouped in 

 2,946 genera and 333 families. h. e. g. 



4. The Erosional History of the Driftless Area; by Arthur 

 C. Trowbridge. University of Iowa, Studies in Natural History, 

 Vol. 9, No. 3, pp. 127, figs. 35, 1921.— The contribution of Pro- 

 fessor Trowbridge to the knowledge of the unglaciated "island" 

 surrounded by glacial drift and lying at the junction of the 

 States of Illinois, Iowa, Wisconsin, and Minnesota is interesting 

 in method and conclusions. Part I is an analytical discussion 

 of the principles of multiple erosion cycles in which the value of 

 ''sets of evidences" is emphasized. "The total number of dis- 

 tinguishable cycles is the number of sets of evidences plus one." 

 In Part II, the author applies his principles in writing the physi- 

 ographic history of the "driftless area" as a whole after detailed 

 study of its parts. The events are : formation at the close of the 

 Paleozoic era of an anticline, the south limb of w^hich was a mono- 

 clinorium; making of the Dodgeville plain or peneplain in late 

 Tertiary time ; followed by an uplift of about 180 feet ; making 

 of the Lancaster peneplain in pre-Kansan Pleistocene ; uplift of 

 600 feet inaugurating a third cycle of erosion which with various 

 episodes continues to the present. 



5. Geological Survey of Western Australia; A. Gibb Mait- 

 LAND, Government Geologist. — The Annual Progress Report 

 of the Western Australia Geological Survey for 1919 (48 pp., 

 1 map) is chiefly a record of reconnaisance in areas from 

 which minerals of economic value have been reported. Sum- 

 mary reports are given for the goldfields on Coolgardie, Yal- 

 goo, Yilgarn, Mont Margaret, Murchison, including the newly 



