April 22, 1909] 



NATURE 



south to south-west prevail, which are explained by 

 the distribution of the isobars. 



Another campaign from July to October, 1907, gave 

 the same general results, as well for the direction 

 of the atmospheric currents as for the vertical distri- 

 bution of temperature (Figs. 2 and 4). This voyage 

 was not continued further south than 10° N., but the 

 vessel remained twice during twelve days near this 

 parallel, this latitude having Ijeen selected on account 

 of the regularity of the trade wind. Again the easterly 





it appears that the altitude at which the tempera- 

 ture ceases to decrease is much greater near the 

 equator than in moderate latitudes. This distribution 

 of temperature is also confirmed for the regions of 

 the .\zores and Canaries, as far as about 25° N., by the 

 ascensions of hallons-sondes made by Prof. Hergesell. 



Our conclusions concerning the direction of the 

 upper currents correspond in substance with former 

 ideas about the anti-trades, apart from the situations 

 which produce currents of very different and almost 

 opposed directions lying one above the other. This 

 new and unexpected fact, which was also observed 

 at Trappes in the barometric maxima of our own 

 regions, agrees tolerably well with certain of Maury's 

 theories. Also near the equator it can be distinctly 

 seen that a portion of the anti-trade comes from the 

 opposite hemisphere. 



Finally, it may be said that, if the exploration of 

 the high atmosphere over the Atlantic does not show 

 a different circulation from that already supposed, at 

 least in its main features, it emphasises the import- 

 ance of superposed strata flowing in various direc- 

 tions, which appear to persist in the regions where 

 cyclonic disturbances of large diameter rarely form. 

 VVe shall attempt later to give an explanation of the 

 superposition of two or three strata having different 

 directions ; but the stratification of numerous thin 

 currents, varying in their motions, is a fact worthy 

 the attention of meteorologists, for we must recognise 

 that to-day no theory explains this special mode of 

 circulation which extends over a very large region. 

 This is certainly one of the important facts brought to 

 light by the three cruises of the Otaria. 



L. Teisserenc de Bort. 

 A. Lawrence Rotch. 



Fig. 4.— Motii 

 J^oie. — In all the figures the i 



n of air in the atmosphere in the region of the Azores. 

 umbers give the altitude and the breadth of the lines th- 



current predominated at all heights, and also the layer 

 of inverted temperature near 1000 metres. 



The ballon-sonde ascensions made in 1907 were 

 somewhat higher than before, and the isothermal 

 layer was reached at 14 kilometres in latitude 

 25° 18' N. North of 25° the isothermal layer 

 was often met with at altitudes varying from 

 12 to 14 kilometres, while to the south of this 

 parallel it was not reached, although the balloons 

 many times exceeded 15 kilometres. Therefore, 

 NO. 2060, VOL. 80] 



AVIATION. MATHEMATICAL AND 

 OTHERWISE.^ 



THE second volume of Mr. Lanchester's farge 

 work deals mainly with the following points : — 

 The forms of the paths described by bodies in free 

 flight ; the conditions of longitudinal, lateral, and 

 directional stability; the theory and use of scale- 

 models ; theories of soaring flight ; and a large 

 number of experimental verifications. 



The theoretical discussions are based, to a large 

 extent, on the consideration of what the author calls 

 phugoid curves. According to the " Glossary, " 

 " phugoid theory " means " the theory dealing with 

 the longitudinal stability and the form of the flight 

 path," though in a footnote the author raises some 

 doubt as to the appropriateness of the Greek deriva- 

 tive which he has himself coined. The simplest 

 form of phugoid curve, to the study of which the 

 author devotes considerable attention, 

 might form the subject of problems 

 that would delight the heart of the 

 old-fashioned tripos examiner. Like 

 the latter's particle on his perfectly 

 smooth surface, the gliding body is 

 ;ity of supposed to have its mass concen- 

 trated at a single point and to travel 

 without loss of energy, and the sup- 

 porting surface is supposed to be small and to 

 be always tangential to the direction of motion. 

 In other words, the problem reduces to that of a 

 particle acted on by gravity and by a supporting 

 force (due to the air) which is always normal to the 



1 (i) ".\erodonetics." Constituting the Second Volume of a complete Worlc 

 on Aerial Flight. Bv F. W. Lanchester. Pp. xvi+433. (London : A. 

 Constable and Co., Ltd, tQo8.) Price t/. ij. net. 



(2) " Artificial and Natural Flight." By Sir Hiram S. Maxim. Pp. xv4- 

 166. (London : Whittaker and Co., 1908.) Price 5s. net. 



