72 H. I. JENSEN, 



Lockyer in his researches has arrived at the result that 

 all Malaysia and Australia follow short period barometric 

 variations exactly similar to those at Bombay, whereas 

 Cordoba in Soutli America has the conditions reversed, and 

 many of the North American towns follow the Oordoban 

 variations. We are told by Professor Bigelow, who comes 

 to the same conclusions as Dr. W. J. S. Lockyer, that the 

 values do not exactly cancel one another ; the Bombay 

 area is much the larger, comprising most of Asia, Europe, 

 part of North America, and all of Australia ; hence Prof. 

 Bigelow thinks " that some external force is at work to 

 i-aise and Joiver the total atmospheric pressure b y a small 

 amount each year.'' 1 Assuming that the small period 

 variations, which Dr. Lockyer discusses, correspond in 

 extent with longer period variations, we may conclude that 

 the excess of pressure above normal at Bombay, and 

 throughout the area which follows tlie Bombay type of 

 variations, does not counterbalance the deficiency in the 

 Cordoban area in a year of sunspot minimum. The reverse 

 would hold under sunspot maximum conditions. 



What then can thus minimise the total atmospheric 

 pressure in years of sunspot maximum and raise it in years 

 of minimum? Evidently the answer is, "variations in 

 total heat and energy received from the sun." When 

 more solar energy is received the earth's atmosphere 

 undergoes a voluminal expansion, which by increasing the 

 height of our atmosphere also increases the effect on it of 

 centrifugal force, and hence lessens the influence of gravity 

 and the pressure at the surface. When less energy is 

 received, the atmosphere undergoes contraction and pres- 

 sure increases. 



We have only got to examine our own Australian meteor- 

 ology to find ample illustration. During sunspot maximum 

 years, such as 1893, 1894, 1895, 1896, far more cyclonic 



