January 27, 19 16] 



NATURE 



605 



across the Gulf. Some birds, as, for instance, the 

 American redstart {Setophaga ruticilla), cross on a 

 front of more than 2000 miles from east to west. 

 Others again cross on a narrow front, as in the case 

 of the red-breasted grosbeak {Zamelodia ludoviciana), 

 which, although the breeding range has a width of 

 2500 miles from east to west, converge, until they leave 

 the United States along a line of Gulf coast only 800 

 miles wide. 



One of the most interesting of the species treated of 

 in this work is the bobolink {Dolichonyx oryzivorns). 

 Our author tells us that " in the case of the bobolink 

 the evolution of a new extension of the migration 

 route is now occurring before our very eyes. By 

 nature a lover of damp meadows, the bobolink was 

 formerly cut off from the western States by the inter- 

 vening arid region. But with the advent of irrigation 

 and the bringing of large areas under cultivation, little 

 colonies of nesting bobolinks are beginning to appear 

 here and there almost to the Pacific," an excellent 

 demonstration of the intimate relation between 

 ecological conditions and geographical distribution. 

 These individuals are stated to " return over the old 

 route and show no disposition to shorten the flight by 

 direct trip across New Mexico to the Gulf coast of 

 Texas." The author, however, like many other 

 writers on this subject, seems too prone to believe that 

 most birds that pass are necessarily recorded. This, 

 however, is absolutely impossible, even on a small and 

 confined space ; how much more so on a great con- 

 tinent such as America? The remarks on the red-eyed 

 vireo {Vireosylva olivacea) as an example of a recent 

 extension of breeding range and consequent elongation 

 of migration route are of much interest. The extra- 

 ordinary overseas flight of the American golden plover 

 {Charadriiis dominicus) in autumn is also referred to, 

 as well as the curious elliptical form its migration 

 takes at that season, the spring route being quite 

 different from that of the autumn. Another most 

 interesting and less known example of an elliptical 

 migration route is that of the white-winged scoter 

 {Oidemia deglandi), of which a full description and 

 map are given. Mr. Cooke also directs attention to 

 relative speed of various species on northward niigra- 

 "'on ; as an example of slow and uniform migration 

 instances the black and white warbler (Muioiilta 



iria), to which he assigns an average speed of 

 twenty-five miles a day during its northward passage 

 from Florida to its breeding places in south-eastern 

 Canada. On rhe other hand, as an example of rapid 

 migration, the grey-cheeked thrush (Hvlocichla 

 aliciae) is instanced, this bird being allotted a speed of 



,0 miles a day for its journey of approximately 4000 

 ■les; in the last part of the route, however, the speed 



- much greater than in the Mississippi valley. Another 

 point touched on is. the condition in which birds arrive 

 at the end of a long migration flight, and the conclu- 

 sion arrived at is that birds are not exhausted by their 

 aerial journeys. This is, no doubt, largely the case in 

 the western hemisphere, where the migratory move- 

 ments are mainly performed overland from the equator 

 to the Arctic regions ; but in the Old World, especially 

 in the British Isles, the migrants arriving after over- 

 seas flights often suffer much from exhaustion, even 

 when the journey has been accomplished under the 

 most favourable weather conditions. In this and in 

 other respects, Mr. Cooke's work affords interesting 

 comparisons between migration phenomena as observed 

 in North America and in the British Isles. 



Our author believes that food supply is the primary 

 cause of migration ; he says the " conclusion is inevit- 

 able that the advantages of the United States and 

 Canada as a summer home, and the superb conditions 



f climate and food for the successful rearing of a 



• stful of voracious young, far overbalance the hazards 

 XO. 2413, VOL. 96] 



and disasters of the journey thither. For these period- 

 ical trips did not just happen in their present form ; 

 each migration route, however long and complex, is 

 but the present stage in development of a flight that 

 at first was short, easily accomplished, and free from 

 danger. Each lengthening of the course was adopted 

 permanently, only after experience through many gene- 

 rations had proved its advantages," a sound statement, 



^nd one that is often in danger of being forgotten. 

 Many other important points are dealt with in Mr. 

 Cooke's pamphlet, but enough has been said to indi- 

 cate its comprehensive and valuable nature : it should 



1 be read by all who are interested in the subject. 



I W. E. C. 



SOLVENTS AND SOLUTIONS.^ 



^pHE appearance of each volume published by the 

 -*■ Carnegie Institution of Washington induces in 

 us a feeling of envy towards our American confreres on 

 account of the facilities thereby afforded to them for 

 the publication in collected form of the results of 

 investigations which otherwise would appear only in 

 small instalments and scattered throughout the various 

 volumes of scientific journals. Through the appear- 

 ance in such a collected form of the results obtained 

 in a series of investigations bearing on one main ques- 

 tion, it becomes possible for other scientific workers 

 to realise more clearly the actual extent of the advance 

 made. For such publications as the present, therefore,, 

 all workers on solutions will be grateful. 



The present monograph deals with a wide variety of 

 subjects, nearly all of them, however, suggested by the 

 solvate theory of solution so familiarly associated with 

 the name of the chief author of this publication. 



In the ten chapters into which the discussion is sub- 

 divided, we find the following subjects dealt with : — 

 Viscosities of solutions of caesium salts in mixed sol- 

 vents ; conductivities of formamide solutions ; radio- 

 metric measurements of the ionisation constants of 

 indicators ; influence of salts on the velocity of saponi- 

 fication and on the hydration of acetic anhydride ; con- 

 ductivity of organic acids in ethyl alcohol ; conductivi- 

 ties and dissociation of some rather unusual salts in 

 aqueous solution ; the dissociating powers of free and 

 of combined water ; the absorption of potassium from 

 aqueous solutions of potassium chloride. 



Of the different contributions, the most interesting 

 are, perhaps, the two dealing with the radio-metric 

 measurements of the ionisation constants of indicators. 

 By means of a grating and a radio-micrometer, of 

 which a description is given, the light transmitted by 

 solutions of methyl-orange and of rosolic acid have been 

 determined. From these determinations the ionisation 

 constants of the indicators could be calculated. In 

 view of the excellent apparatus which the authors 

 possess, further valuable work on a difficult problem 

 may be hopefully expected. A. F. 



THE FRUITS, PROSPECTS, AND LESSONS 

 OF RECENT BIOLOGICAL RESEARCH.' 



HE general welfare of mankind has been wonder- 

 fully promoted during the past 150 years by the 

 rapid progress of chemical, physical, and biological 

 science. In the early third of that period, physics 

 and chemistry and their applications seem to have 

 plaved the most active parts in promoting human 

 welfare, although pure botany and zoology enlisted 



1 " Conductivities and Viscosities in Pure and in Mixed Solvents. Radio' 

 metric Measurements of the Ionisation Constants of Indicators." By H.C- 

 Jones and Collaborators. Publication No. 230. (Washington D.C.- 

 Carnegie Institution, iqis.) 



- Presidential address delivered to the American Association for the 

 Advancement of Science at Columbus, Ohio, on December 27, 1915, by 

 Dr. Charles W. Eliot. 



J, 



