444 



SCIENCE 



[N. S. Vol. LIII. No. 1375 



It will be wortli wMle, therefore, in these 

 notes to give the salient features of the 

 Bjerknes papers.* 



The Bjerknes Lines of Discontinuity. — The 

 changes of weather which are associated with 

 the passage of highs and lows in the tem- 

 perate zone are found to depend largely upon 

 a line of discontinuity which marks the 

 boundary between polar and equatorial air. 

 In an individual cyclone, this line of discon- 

 tinuity consists of the steering line and the 

 squall- or wind-shift, line. Considering as 

 large a portion of the northern hemisphere as 

 possible, this line of discontiuuity can be 

 traced from one storm to another so that 

 there is little doubt that it is continuous 

 around the world. North of this line the air 

 is that which " has a low temperature for the 

 latitude, shows great dryness, distinguishes 

 itself by gTeat visibility, and has a prevailing 

 motion from east and north. On the southern 

 side of the liae, the tropical origin of the air 

 is recognized by the corresponding signs — its 

 generally higher temperature, its greater 

 humidity, its haziness and its prevailing 

 motion from west and south." This line is 

 called tlie polar-front line. 



Sometimes the undulations of the line are 

 such as to cause loops which may represent 

 the cutting off from the parent mass, masses 

 of warm or cold air depending upon how far 

 north or south the tropical or xwlar air may 

 extend. If the warm air is cut off, the 

 cyclone decreases in intensity and disappears; 

 or, in the case of a new outbreak of polar air 

 a new front is formed behind a too far ad- 

 vanced one; isolated masses of polar air are 

 formed at lower latitudes. This is the forma- 

 tion of great anticyclones, which bring good 

 weather. 



* Bjerknes, J., "On the Structure of MJoving 

 Cyollones, " Monthly Weather Meview, February, 



1919, pp. 95-99; "The Structure of the Atmoa- 

 ptere when Eain is Fallmg" (abstract), ibid., 

 July, 1920, p. 401; Bjerknes, V., "The Meteorol- 

 ogy of the Temperate Zone and the General At- 

 mospheric Oiroulabion, " ibid., January, 1921, pp. 

 1-3; appeared also in Nature (London), June 24, 



1920, pp. 522-524. 



In the case of the individual cyclone, the 

 phenomena along this line of discontinuity are 

 about as follows: That part of the line which 

 lies in a general easterly direction from the 

 center of the cyclone is known as the steering- 

 line. South of it the air is moving from the 

 south; north of it the air is from the east. 

 Along the line the warm southerly air rises 

 over the denser easterly air. Passing through 

 the center of the cyclone the line extends off 

 in a southwesterly direction and forms the 

 western boundary of the warm tongue of 

 southerly air, and the eastern front of an ad- 

 vancing wedge of cooler northwesterly air. 

 This line is known as the squall line; and its 

 passage is frequently accompanied by consider- 

 able violence, with thunderstorms and some- 

 times tornadoes, but usually with only a 

 strong blow, a rise of pressure, a drop of tem- 

 perature, and, of course, a change of wind 

 direction. 



It was on the basis of the advance of these 

 lines of discontinuity that Mr. Andrus was 

 able to predict the path and advise the bal- 

 loonists to make as little westerly progress as 

 possible during the first night, to stay as far 

 east and north as possible, even if it were nec- 

 essary to disregard the usual practise in bal- 

 looning of staying as low as possible to avoid 

 expenditure of ballast early in the race. The 

 winner followed this advice and had landed 

 in Vermont many hours before the others who 

 had reached no gi-eater distance than Illinois 

 and lower Michigan. This fact demonstrates 

 very clearly that, as Mr. TJpson frankly con- 

 fesses and as Mr. Andrus emphatically states, 

 it was meteorology that won the race. 



C. LeEoy Meisinger 



Washixgton, D. C. 



SPECIAL ARTICLES 



THE CATALYTIC PROPERTIES OF THE 

 RESPIRATORY METALS' 



The more important physical and chemical 

 properties of the respiratory metals — iron, 

 copper, manganese and vanadium — have long 



1 Contributions from the Bermuda Biological 

 Station for Eeseareh, No. 123. 



