NA rURE 



421 



THURSDAY, MARCH 30, 1876 



BLASIUS ON STORMS 



Storms ; their Nature, Classification, and Laws, with the 

 Means of Predicting them by their Embodi7ne7its, the 

 Clouds. By William Blasius, formerly Professor of the 

 Natural Sciences in the Lyceuift of Hanover. (Phila- 

 delphia : Porter and Coates. London : Lockwood and 

 Co.) 



WHATEVER may be thought of this work as a con- 

 tribution to the extremely difficult question of the 

 theory of storms, its dehghtful " positiveness of state- 

 ment born of conviction," makes it a very readable book ; 

 and, further, the fresh facts contained in its pages, collected 

 in most cases with evident care, form a useful repository 

 to meteorologists in the study of atmospherical disturb- 

 ances. In matters pertaining to general meteorology, the 

 author is less at home as regards his facts, such as when 

 he states that the heat of the sun's rays scarcely pene- 

 trates an inch into the surface of the land in the course 

 of a day. He is also at fault as regards the seasonal dis- 

 tribution of atmospheric pressure over the globe, and the 

 extent over which the south-west monsoon spreads to 

 westward off the coast of Africa. 



A storm is defined to be " in general the movement of 

 the air caused by its tendency to re-establish an equili- 

 brium which has in some manner been disturbed, and we 

 may call all such movements storms, whether they are 

 gentle breezes or furious hurricanes, whether they are 

 accompanied by more or less condensation of moisture or 

 clouds, or even by none at all ; in general the laws of the 

 motion and changes of the wind in re-establishing an 

 equilibrium must be the same, whether the action takes 

 place in a greater or less degree " (p. 43), and the author 

 " is certain that the storm is the conflict of air-currents 

 of different temperatures, and that the barometric de- 

 pression is the effect of their movement" (p. 5). Thus 

 storms are considered in a very broad sense, — in fact, they 

 are regarded as synonymous with the whole atmospheri- 

 cal movements, and the book is therefore an attempt 

 to state the theory of the circulation of the atmosphere. 



Since the disturbances which occur in the distribution 

 of the temperature and humidity of the air are either ver- 

 tical or horizontal, it follows that the equilibrium will be 

 restored either by the setting in of ascending or descend- 

 ing currents of air, or by the setting in of horizontally- 

 flowing currents. Observation affords abundant proofs 

 of the existence of all these types of aerial movements. 

 In accordance with this conception of atmospherical dis- 

 turbances and consequent movements which follow. Prof. 

 Blasius classes all storms under three heads, viz. : — i. 

 Local or vertical storms, which are stationary and centri- 

 petal, being produced by the atmosphere tending to re- 

 establish in a vertical direction an equilibrium that has 

 been disturbed ; the characteristic cloud being the cumulus. 

 2. Progressive or lateral storins which travel, being pro- 

 duced by the atmosphere tending to re-establish in a 

 lateral direction an equilibrium which has been disturbed. 

 This second class of storms are of two kinds, viz., eqtia- 

 torial or north-east storms (winter storms), which are pro- 

 duced by a warm current displacing a cool one to supply 

 Vol. XIII,— No. 335 



a deficiency towards the poles, the temperature changing 

 from cool to warm, the direction in which they travel 

 being to the north-east quadrant, and their characteristic 

 cloud being the stratus. Polar or sotith-east and south- 

 west storms (summer storms), which are produced by a 

 cool current displacing a warm one to supply a deficiency 

 toward the equator, the temperature changing from warm 

 to cool, the direction in which they travel being to the 

 southern semicircle, and their characteristic cloud being 

 the cumulo-stratus. 3. Loco-progressive or diagonal 

 storms (tornadoes, hail-storms, sand-storms, waterspouts, 

 &c.), which travel locally, are rotator)', and are produced 

 by the atmosphere tending to re-establish the equilibrium 

 of a polar storm which has been disturbed in the plane of 

 meeting of the two conflicting currents by a peculiar con- 

 figuration of the ground, their characteristic cloud being 

 what the author calls the conus, instances of which are 

 presented by the funnel-shaped cloud of waterspouts. 



In the explanation offered of the most important of 

 these classes, viz., the winter storms, their origin is attri- 

 buted to an assumed distribution of atmospheric pressure 

 from the equator to 80° lat. N., and to the polar and 

 equatorial currents which result from this distribu- 

 tion of pressure, and which conflict with each other — the 

 shifting of the atmosphere with the motion of the sun 

 toward the north during spring and summer and toward 

 the south during autumn and winter, taking place not 

 regularly, but interruptedly, by repeated oscillations hke 

 the waves of the rising and falling tide. In the winter 

 storm there is an area of lowest barometer marking the 

 region where the equatorial current overlaps the polar 

 current and the theatre of the cloud and rain which 

 accompany the storm, with two regions of high barometer, 

 one in front and the other in the rear of it. These three 

 regions move forward thus : — The region of high baro- 

 meter, which apparently moves far in front of the storm, 

 is the receding polar current ; the region of low baro- 

 meter, the uprising current ; and the region of high baro- 

 meter, in the rear of the storm, the in-blowing equatorial 

 current. It is asserted that the area of the storm, or the 

 region of conflict between the equatorial and the polar 

 currents, must assume the form of an ellipse, and not that 

 of a circle, and that the air in a storm does not move 

 around one centre, much less around the line when the 

 plane of meeting of the polar and equatorial currents 

 meet the earth's surface, but in straight lines from the 

 circumference of the ellipse toward the region of the up- 

 rising equatorial current The progressive velocity of the 

 storm depends on the greater or less resistance with which 

 the polar current opposes the displacing equatorial cur- 

 rent, since the greater this becomes during the develop- 

 ment of the storm, the more the plane of meeting must 

 rise or approach a vertical position, and thus the pro- 

 gressive velocity of the storm be proportionally retarded. 



It is unnecessary to follow Prof. Blasius through his 

 theory of the atmospheric movements comprehending our 

 winter storms, which we have stated as far as possible 

 in his own words. It may be enough to point out that at 

 least those regions of the globe with whose meteorology 

 Prof. Blasius does not appear to be very familiar, present 

 facts not in accordance with his theory, proving that 

 storms do not necessarily arise from great currents which 

 can be traced to equatorial or sub-tropical regions on the 



