146 NATURAL SCIENCE [September 



of the interesting problems connected with the history of the Arctic 

 regions. In the first paper, a summary is given of the geological 

 structure of the land masses surrounding the Arctic Ocean ; the 

 variations in the relative positions of land and water are traced, and 

 it is argued that the Polar Basin has been formed by subsidence 

 during Tertiary times. In the second paper, the author considers 

 the changes in climate that have taken place in the North Polar 

 Regions. He refers to the famous theory according to which the 

 Arctic regions were once clothed in tropical vegetation and their 

 shores were once fringed by coral reefs. The evidence on which 

 this theory rests is, however, shown to be very untrustworthy. The 

 plant determinations made by Heer are unreliable, and there is no 

 evidence that coral reefs were ever formed within the Arctic Circle. 

 Corals grew in Arctic seas in earlier times as they do to-day, but 

 there has been no adequate proof that they ever formed reefs. Dr 

 Gregory accordingly distrusts all the theories as to the great size of 

 the sun in Palaeozoic times and the universal uniform climate in 

 the pre-Tertiary period, which have been based on the asserted 

 Arctic palm-groves and coral seas. That climatic changes have 

 occurred is not disputed, but the author does not think it possible 

 to estimate their extent until the palaeontology of the Arctic regions 

 has been carefully revised. The most important work on this 

 subject now being carried on is Professor Nathorst's redescription of 

 the fossils about which Heer theorised so wildly. Dr Gregory also 

 concludes that palaeontological evidence tells strongly against the 

 view that the position of the Poles has altered to any great 

 extent. 



BlliDS AND THEIE STOMACHS 



The United States Department of Agriculture, knowing that the 

 welfare of the country depends largely on the prosperity of the 

 farming class, has undertaken for long past a proper . consideration 

 of birds in their relation to agriculture. In its fifty-fourth bulletin 

 it deals with the stomach-contents of some twenty common birds. 

 Among these may be mentioned the cuckoos, woodpeckers, bluejays, 

 ricebirds, blackbirds, orioles, cedarbirds, catbirds, bluebirds, &c. 

 There is a good deal of practical common-sense in the introduction 

 of this pamphlet by Mr P. E. L. Beal, who points out the tendency 

 to dwell on the harm done by birds rather than the good. He goes 

 on to say : — 



" Within certain limits, birds feed upon the kind of food that is 

 most accessible. Thus, as a rule, insectivorous birds eat the insects 

 that are most easily obtained, provided they do not have some 

 peculiarly disagreeable property. It is not probable that a bird 



