MARCH 4, 192.1 abstracts: ornithology 11 



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ORNITHOLOGY. — The migration of North American birds. XI. Canada 

 Jay, Oregon Jay, Clarke's Nutcracker, and Pifion Jay. Harry C. 

 Oberholser. Bird Lore 21: 354-355. 1919. 



From data chiefly in the United States Biological Survey the geographic 

 distribution and movements of four species of Icteridae have been deter- 

 mined. Five subspecies of Perisoreus canadensis are recognized, including 

 the recently described Perisoreus canadensis sanfordi and three forms of 

 Perisoreus obscurus, including Perisoreus obscurus rathbuni. Data on Nuci- 

 fraga columbiana and Cvanocephalus cyanocephalus are also given. 



H. C. O. 



PHYSICAL CHEMISTRY. — Estimating impurities by means of the melting 

 point curve. W. P. White. Journ. Phys. Chem. 24: 393-416. 1920. 



Freezing points where the thermometer is immersed in the substance are 

 more reliable and precise than those by the capillary tube method. If in 

 addition the form of the freezing curve is observed, there is obtained an in- 

 dication of the amount of impurity, which is independent of all previous 

 knowledge or uncertainty as to the melting point of the pure substance, and 

 even of the absolute accuracy of the observer's thermometer. 



Smallness of dimensions diminishes local temperature differences, and 

 is very often a superior substitute for stirring of the tested substance. It 

 also economizes both time and material. The complications, usually almost 

 negligible, arising from specific heat, uneven temperature, and other causes 

 are considered, and suitable experimental arrangements are suggested. 



W. P. W. 



