abstracts: ornithology 207 



VOLCANOLOGY. — Persistence of vents at Stromholi and its hearing on 

 volcanic mechanism. Henry S. Washington. Bull. Geol. Soc. 

 Amer. 28: 249-278. March, 1917. 

 In August, 1914, six vents were active on the crater terrace of Strom- 

 boli. Examination of plans and illustrations in the literature (many 

 of which are reproduced in the paper) shows that at least three of 

 these vents have persisted in location as far back as 1768. Similarly, 

 at Kilauea the main vent has persisted in location for about a century;' 

 and there is evidence of such persistence at some other volcanoes. 

 This feature of volcanoes seems to have been previously unnoticed. 

 Another notable feature of the Stromboli vents is that the oldest 

 three of them open about *1 000 meters above sea-level near the upper 

 edge of a precipitous scarp of that height. An analogous situation is 

 true of some of the vents at Etna and also of one or two of those of 

 Kilauea. 



In the discussion of these and other features it is shown that such 

 vents can not have originated through explosive agencies; but that 

 their formation, situation, persistence in location, and other features 

 can best be explained by Daly's so-called "gas-fluxing hypothesis," 

 which supposes a "blow-piping" of narrow, vertical vents through the 

 superjacent rocks by hot gases derived from the magma in its reservoir 

 below and kept hot by chemical interreactions. • H. S. W. 



ORNITHOLOGY.— 7'/!e migration of North American birds. 1. Five 

 sicallows. Harry C. Oberholser. Bird-Lore 19 : 320-330. De- 

 cember 1, 1917. 

 In this article there are given tables of migration dates for both 

 spring and fall, chiefly from the United States and Canada, of the five 

 following species of swallows, together with the subspecies of each: 

 Petrochelidon lunifrons (lege albifrons), Iridoprocne bicolor, Tachy- 

 cineta thalassina, Riparia riparia, and Stelgidopteryx serripenyiis. The 

 data given serve as an index to the migratory movements of these 

 species, and include the average date of spring arrival, the earliest 

 date of spring arrival, the average date of last one observed, and the 

 latest date of last one observed, in autumn as well as in spring, together 

 with a statement of the numbers of years of observation on which the 

 averages are based. M. C U. 



