February 4, 1909] 



NA TURE 



397 



memoirs on sjiouus of insects. The first section o{ 

 this volume is by J. Weise, of Berlin, and describes 

 the Chrysomelid;e and Coccinellidas, of which the 

 expedition obtained twenty-eight species, of which 

 nine are new. The second section is by Dr. Bernhauer, 

 and describes the Staphylinidce, and founds eleven new- 

 species, one of which is the type of a new sub-genus. 

 The third section, by Georg Ulmer, of Hamburg, 

 describes the Trichoptera and Ephemeridfe, and in- 

 cludes a synopsis of the Trichoptera known on the 

 -Australian continent. This report is illustrated by a 

 valuable series of drawings in the text. Five new- 

 species are described, and many larval forms. The 

 fourth section, by F. Silvestri, describes the Thysanura, 

 including fifteen species of Lepisma and one of 

 japvgus. Twelve of the species are new, and one of 

 I hem represents a new genus. The report is illustrated 

 by ten plates. 



The volume gives further evidence of the valuable 

 additions to Australian zoology made by Prof. Michael- 

 sen and Dr. Hartmeyer's expedition. 



Lclnbuch der Muskel- und Gelenkmcchanik. By 



Prof. H. Strasser. I. Bd. .Mlgemeiner Teil. 



Pp. xi + 2i2. (Berlin : Julius Springer, igoS.) 



Price 7 marks. 

 This book is the work of one who has made animal 

 mechanics a life-study. Prof. Strasser will be par- 

 ticularly remembered on account of his work, pub- 

 lished some twenty years ago, upon the flight of 

 birds and the swimming of fish. 



The first section of his book — some seventy-three 

 pages — is devoted to an admirable digest of the 

 mechanical principles involved. It is illustrated by 

 ]ilenty of figures. 



The second part is devoted to the skeleton, the 

 luechanical prop ; the movements at the joints ; the 

 different forms of muscle, the angles which the in- 

 dividual fibres make when inserted into bone, and 

 muscle work. 



The third section refers to the general problem of 

 the joints and muscles, and deals w-ith several static 

 problems in the first case, and with locomotion in the 

 second. 



The author has treated the whole subject much as 

 one would treat an ordinary physical problem, in all 

 mathematical detail. He is to be congratulated upon 

 his method and upon the way in which he has carried 

 it out. We believe that there is no treatise in the 

 English language which can be considered as quite 

 on all fours with his book, and we can heartily re- 

 commend its study. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opiniom 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part 0/ Nature. 

 jYy notice is taken of anonymous communications.] 



Diurnal and Semi-diurnal Atmospheric Variations. 



I n.vvE read the remarks of Prof. Horace Lamb in 

 Nature, November 5, 1908, p. 24, and November 12, 1908, 

 p. 47, where, although mentioning difficulties, he appar- 

 ently accepts the suggestions of Kelvin, Margules, and 

 Hann that the semi-diurnal wave of pressure can be ex- 

 plained by the fact that " the daily variation of temperature 

 is not harmonic, and when analysed there is a definite 

 component with a half-day period," and " on a rotating 

 r.irth the period of free oscillation of the atmosphere lies 

 \ ' ly near to twelve hours." 



In connection with this, I wish to direct attention to the 



fact that an analysis of the records of instruments carried 

 by kites shows that the chief oscillation in temperature 

 in the body of the atmosphere is a semi-diurnal one, and 

 not a single oscillation such as is found near the ground. 



In a discussion of the observations obtained with kites 

 at the Blue Hill Meteorological Observatory, published in 

 the annals of the Astronomical Observatory of Harvard 

 College, vol. Iviii., part i., 1904, I showed that the single 

 diurnal oscillation of temperature nearly disappears within 

 300 metres of the earth's surface, and from 500 metres to 

 1500 metres only a semi-diurnal oscillation is distinctly 

 apparent. 



For the method employed the reader must be referred 

 to the publication mentioned. The final results in degrees 

 Fahrenheit were as follows : — 



Normal Diurnal Temperatures at different Levels above 

 Blue Hill. 



39-9 37-9 37-7 39'4 47-9 Si-8 



45-7 46-0 45-6 44-6 43-5 44-1 



40-4 40-4 40-5 40-4 39-3 40-1 



I37'5 36-9 3fi'5 36-8 360 34-5 



53-8 53'9 5i'5 47-2 42-8 41-2: 45'4 



45-8 45-8 44-2 43-2 43-6 44-61 44-7 



40'5 40-4 40-3 40-3 40-0 40'oi 40-2 



35-2 36-4 36-' 34-7 34'9 36-9 36-0 



The harmonic values computed from the observations 

 are as follows, the epoch in each case being midnight : — 



45-4 + 8-33 sin (234+.v)+i-63S 

 44-7+0-47 5in (i3+-f)+i-67 s 

 40-2+0-09 5in (85+.i)+o-35 s 

 36-0 + 0-90 sin (47 + .r)+o-8o s 



1 (73+2-v)+&c. 

 1 (i8+2.r)+&c. 

 i(344 + 2.>-)+S:c. 

 1 Co+2.r)+&c. 



These results show that the amplitude of the single 

 diurnal period near the earth's surface (15 metres above 

 sea-level) is 8°-3 F., but at 500 metres it has decreased 

 to less than half a degree Fahrenheit, and at 1000 metres 

 to less than a tenth of a degree Fahrenheit. At 1500 

 metres the range apparently increases somewhat, but this 

 is perhaps owing to the small amount of data available at 

 that height. The mean of all the daily ranges between 

 500 metres and 1500 metres, inclusive, is slightly less than 

 half a degree. Furthermore, at 500 metres to 1500 metres 

 the phase angle has changed nearly 180° as compared to 

 that at the earth's surface, so that the maximum in the 

 daily wave of temperature comes at night instead of during 

 the day. The reversal of phase apparently takes place 

 between 300 metres and 500 metres. 



Turning to the values in the formula showing the semi- 

 diurnal period, it is seen that at 500 metres and 1000 metres 

 the amplitude is nearly four times as great as is the 

 amplitude of the diurnal period, but at 1500 metres the 

 two appear to be nearly equal. The maxima in tempera- 

 ture are about 3 a.m. and 3 p.m., not far in time from 

 the semi-diurnal minima of pressure, while the minima 

 of temperature are near g a.m. and 9 p.m., not far from 

 the times of the semi-diurnal ma.xima of pressure. 



In commenting on these results in the publication re- 

 ferred to, I say (p. 32) : — " But the fact of particular 

 interest is that the mean of the amplitudes of the semi- 

 diurnal period from 500 to 1500 metres, thus including 

 the larger portion of the lower atmosphere, is greater than 

 the mean amplitude of the diurnal period. This fact is 

 of interest in connection with the views of Lord Kelvin, 

 Dr. Margules, and Dr. Hann concerning the cause of 

 the semi-diurnal wave." 



In '905 Prof. Frank H. Bigelow, analysing the data 

 obtained at Blue Hill more in detail and by a method 

 somewhat different from my own, confirmed the existence 

 of the semi-diurnal period of temperature in the body of 

 the atmosphere. He says : — " The single diurnal period 

 at the surface is replaced by a double diurnal wave at 400 

 metres, and this appears quite plainly in every month 

 except July, where it is probably nearly extinct " (Monthly 

 Weather Review, 1905, p. 55). 



The existence of a maximum of temperature by day and 

 a secondary maximum at night, with a diurnal amplitude 

 of about i°-3 C. at a height of 1200 metres above Hald, 

 Denmark, has also been disclosed by W. Wundt in an 

 analysis of the observations made with kites at that 

 station (Meteorologische Zeitschrift, 1908, pp. 337-41). 



NO. 2049, VOL. 79] 



