368 



NATURE 



[September 22, 1910 



the importance of sexual as opposed to natural selec- 

 tion, and believes that the latter, working on the dis- 

 continuous variations which undoubtedly occur, tends 

 to preserve those varieties which finally persist. 



Nidification and incubation, eggs and young, and 

 the care of the latter, are next considered, while Mr. 

 Pycraft has much to tell us of what we may learn 

 from the immature bird, whether in the embryonic 

 stage or otherwise, of its precocity or helplessness, its 

 downy condition, its seasonal changes, and its differ- 

 ences from the adult. We notice that he thinks that 

 nest-building is "a product of selection and is in- 

 stinctive," and that all eggs were perhaps originally 

 white and assumed protective coloration only where 

 necessary. 



Artificial varieties and the question of in- 

 heritance of acquired characters are treated by 

 the author at some length, while his natural 

 bent towards anatomv enables him to deal fully and 

 successfullv with the interesting and important sub- 

 jects of structural and functional adaptations, and to 

 conclude a work, which we heartily commend to our 

 readers, with a detailed account of various instances 

 of homoplasy. 



The numerous illustrations, some of which are new, 

 add much to the value of the book. 



REFORMS OF THE CALENDAR. 



IN the August number of Flimmel luid Erie, Prof. 

 Forster has a paper on calendar reform, on wiiich. 

 though it is rather discursive, a few words may be of 

 interest. The main point of the paper is to suggest 

 that the International Congress of Chambers of 

 Commerce should take up the question of altering 

 the rule for keeping Easter, which has, from the 

 beginning of the Christian Church, been regulated 

 by luni-solar chronology. That sort of chronology was 

 observed over a large part of Asia, and is by the Jews 

 to the present day, making the year consist of twelve 

 and thirteen months alternately, the months following 

 the moon. But, of course, this does not make the 

 correspondence exact, and other intercalations were 

 niecessarv. The old Roman calendar was also luni- 

 solar, the months being made to contain twenty-nine 

 and thirty days alternately, which would give only 

 354 days in a year, so that an additional or intercalary 

 month had to be inserted in alternate years of varying 

 length. 



As Dr. Forster remarks, the old Roman calendar 

 had degenerated into a true monster of chronological 

 complication ("zu einem wahren Monstrum von 

 chronologischer Verwirrung "), when it occurred to 

 Julius Caesar that it would be best to discard the moon 

 altogether as a time-measurement and regulate the 

 calendar by the sun, as had been done in the old 

 Egyptian chronology, a country in which the annual 

 overflow of the Nile was of surpassing importance, 

 and, of course, depended on the solar season. 



Casar had no occasion to trouble about the days of 

 the week in his calendar. All European nations have 

 followed in the main his calendar, but have had to 

 make a special case of the great Easter festival and 

 the ecclesiastical dates depending on it. But there is 

 no real necessity for falling back upon a Jewish or luni- 

 solar method of reckoning in this respect. 



In the years 1872 and 1873 the Rev. J. Newland 

 Smith, of Greenwich, published and distributed two 

 pamphlets on "Eastertide," pointing out that the 

 present complicated rule for keeping Easter was not 

 fixed by any Church regulation ; the Council of Nicjea 

 having only decided that it should always be kept on 

 a Sunday. Had Mr. Newland Smith lived (he died 

 in 18S0) he hoped that a Bill would have been intro- 



NO. 2134, VOL. 84] 



duced into Parliament on the question. The proposal 

 in his first pamphlet was that Easter should be kept 

 either on April 9 (that being one probable date of 

 the first Easter day}, if that day were a Sunday, or. 

 if not, on the following Sunday; in the second, that 

 it should be always kept on the second Sunday in 

 April, which would include the gth. 



Dr. Forster, in the article before us, makes a similar 

 proposition, which he commends to the International 

 Congress of Chambers of Commerce, that Easter 

 should be kept on the Sunday following April 4, so 

 that it would always fall between the 5th and iith. 



He hopes that other changes may be effected in tne 

 calendar, and particularly that the congress may be 

 the means of inducing the Russians and the Greek 

 Church generally to follow the Western usage and 

 replace the Julian by the Gregorian calendar, or some 

 modification of it. 



Perhaps we may be allowed the suggestion that the 

 dropping of a leap year each 128th year would be both 

 more convenient and more accurate than the existing 

 Gregorian rule. \\'. T. L. 



THE DYNAMICS OF FOHN.' 



MUCH has been written about the dynamics of 

 Fohn, and the general principles involved 

 in it are well understood, yet the processes by which 

 an air current descends and displaces potentially 

 colder air are still somewhat obscure. As in his 

 previous studies of the same subject. Dr. Ficker has 

 followed the method of examining in detail a large 

 number of individual cases. The process is a laborious 

 one, but w'e agree with the author that it is essential 

 to follow out individual cases if we wish to arrive 

 at a clear understanding of the processes involved. 

 Average results may be very misleading ; very prob- 

 ably the condition of things represented by averages 

 never actually occurs. 



In all cases examined, Fohn was preceded by typical 

 anticyclonic conditions, with a very stable stratification 

 of the atmosphere. In many instances the valley tem- 

 peratures were actually lower than those observed 

 simultaneously on the summits. Special attention was 

 given to the time of commencement of Fohn at 

 different stations, which can be accurately determined 

 from thermograph traces. Fohn sets in earliest at the 

 high stations at the head of the valleys, and makes 

 its way gradually to lower levels. Stations at the 

 same altitude experience the onset of Fohn approxi- 

 mately simultaneously, even though they be in 

 different valleys. In a few instances, Fohn made its 

 appearance at Hachlaching, a station near Munich, on 

 the Bavarian plateau, but on all such occasions the 

 outbreak occurred there long after Fohn had estab- 

 lished itself in the higher valleys. The suggestion 

 that barometric minima skirting the north-west coast 

 of Europe exert an aspirating action on the lower 

 strata of the atmosphere, and so cause the Fohn, thus 

 falls to the ground. 



Local conditions determine the outbreak of Fohn. 

 During the continuance of anticyclonic conditions the 

 valleys become filled with a mass of more or less 

 stagnant air, cold, at any rate in winter, by reason 

 of its contact with the mountain sides, which are 

 chilled bv radiation. Above this we find a region of 

 potentially warmer air, and at the junction of the 

 two layers there is often a sudden actual increase of 

 temperature with altitude. The cold air drains away 

 to lower levels. This process is accompanied by a 

 gradual rise of temperature, but the winds associated 

 with it cannot be regarded as true Fohn, because the 

 vertical temperature gradient in them is much less 



1 " Innsbrucker Firhnsludien IV. Weitere BeilrS^e ziir Dynamite der 

 FShns." By Dr. H. v. Ficl<er. Pp. 6i. (Wien : Alfred Holder, 1910.) 



