142 



SCIENCE. 



LVoL. I., No. 5. 



adopting the doctrine of the dissipation of solar 

 energj", and citing the paleontologic evidence 

 of warm tertiarj^ climates in arctic regions. 



Search is made for proofs of recent changes 

 of temperature corresponding to the recent 

 changes in precipitation. The thermometric 

 record is rejected, because the conditions of 

 observation have not been constant ; but cer- 

 tain circumstantial evidence is admitted. The 

 northern limit of the grape and other cultivated 

 plants is observed to be now farther south than 

 formerlj', and the northern limit of human 

 habitation has been crowded somewhat south- 

 ward. The people of Greenland and Iceland 

 are emigrating, and icebergs are multiplying 

 in arctic waters. 



This theory of the continuous fall of general 

 temperature is evidentlj' inconsistent with the 

 prevalent assumption that the glacial epoch 

 was a 'period of exceptional cold, and a con- 

 siderable share of the book is devoted to the 

 setting-aside of that assumption. To this end 

 the present glaciation of the earth is reviewed 

 at some length, and the conditions of glacier 

 formation are discussed. It is shown that 

 mere cold, whether it pertain to high latitude 

 or to high altitude, is not sufficient, but that 

 an abundant precipitation must accompanj' it ; 

 and, since a lowering of general temperature 

 tends to check precipitation by checking evapo- 

 ration, it should not be predicated as the cause 

 of the glacial epoch. A higher general tem- 

 perature is quite as likely to be a favorable 

 condition for producing the demonstrated 

 effects. 



For a series of decades there has been a 

 genei'al shortening of the glaciers of the Alps, 

 the Caucasus, and the ]P3'renees. In some 

 localities the retrograde movement began about 

 fiftj- years ago ; in others, twenty-five ; and the 

 longer glaciers have receded several thousand 

 feet. This is ascribed to a slight diminution 

 of precipitation, caused by the general cooling 

 of the atmosphere, and is correlated with the 

 desiccation of the shores of the Mediterra- 

 nean. 



The phenomena of the glacial epoch are then 

 reviewed ; and it is stated that only in western 

 Europe and north-eastern America was the 

 glaciation so extensive as to demand the 

 assumption of conditions considerablj' different 

 from the present. The environments of indi- 

 vidual glacier districts are discussed, and the 

 prevalent ideas with reference to the magni- 

 tude of the phenomena of the glacial epoch are 

 combated. 



In particular are the phenomena of Green- 

 land, Scandinavia, and the Ural contrasted. 



Precipitation is now small in the district of the 

 Ural, large in Scandinavia, and probably large 

 in Greenland. This accounts for the extensive 

 glaciation of Scandinavia and Greenland, and 

 the absence of glaciers, both ancient and mod- 

 ern, from the Ural. The present conditions 

 of Scandinavia and Greenland differ chieflj' in 

 that the latter is somewhat higher and more 

 maritime ; and to account for the ancient ex- 

 treme glaciation of Scandinavia, it would be 

 natural to suppose that it then resembled 

 Greenland in these respects. According to 

 the Swedish geologists, this was the case. Its 

 altitude was greater, and during at least a 

 portion of the glacial epoch the plain at its 

 eastern margin was submerged. 



The description of the glaciation of north- 

 eastern America is somewhat meagre, and is 

 chiefly' characterized by a tendency to estimate 

 lower than other geologists the magnitude of 

 the phenomena. The existence of an ice-sheet 

 is not denied ; but the difficulties attending 

 the glacial h3'pothesis are emphasized, and 

 great importance is attached to the work of 

 icebergs and rivers. 



Incidentally the book is replete with illustra- 

 tions of the independence of the author's opin- 

 ions. He ascribes no erosive power whatever 

 to glaciers, but refers the multitudinous rock 

 basins of Canada and Finland to chemical 

 decomposition and orographic displacement, 

 and asserts that the tendencj' of streams is 

 to deepen these basins rather than obliterate 

 them. He has a theor}'' of glacier-motion in 

 which water plays an important part ; and he 

 ridicules the idea that different laj-ers of a 

 confluent ice-mass can move in different direc- 

 tions. The statement that most, if not all, of 

 the detrital material of north-eastern North 

 America is destitute of an}' true morainic 

 character, will sound strange to the geologists 

 who are now studying the moraines of that 

 region. 



In a succeeding number some of the author's 

 more comprehensive conclusions will be dis- 

 cussed. 



THE GOVERNMENT AGRICULTURAL 

 REPORT. 



Report of the commissioner of agriculture for the 

 years 1881 and 1882. Washington, Government 

 printing-office. 1882. 704 p., 84 ph 8°. 



Inasmuch as the present commissioner, when 

 he entered u]30n his duties, "found the vrork 

 for the season, both regular and special, elabo- 

 rateh' laid out by my [his] successor," his 

 report not unnaturall}' bears a strong resem- 

 blance to the reports of preceding years. It 



