l68 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 70 



phere, probably in the cloud-building layers. He draws this con- 

 clusion because the air pressure anomalies for the time of high pres- 

 sure between May, 1876, and August, 1878, was considerably greater 

 in the Himalayas at 6,900 feet than in the interior plains of Bengal. 

 He furthermore draws the same conclusion from the fact brought out 

 by Gautier and Koppen that the temperature of the atmosphere at 

 the earth's surface varies in such a manner that it stands in opposite 

 relation to the air pressure variation. On the one hand high tem- 

 perature with high air pressure prevails at sun spot minimum, while 

 at sun spot maximum low temperature and low air pressures prevail. 

 He conceived it probable that the most important factor producing 

 the observed diminution of air pressure at sun spot maximum is the 

 increase of evaporation and the uprising of water vapor, which may 

 produce effects of three kinds: First, that the water vapor displaces 

 air whose density is three-eighths times greater; second, because 

 the heat of condensation is set free in the higher layers ; and third, 

 because of the upward rising currents which may diminish the pres- 

 sure of the atmosphere in a purely dynamical way. The first and 

 second of these processes would not directly diminish the air pres- 

 sure, but only the density of the air layer and thereby only increase 

 its volume, but in this way a part of the upper atmosphere must be 

 displaced and it would necessarily flow over into regions where the 

 water vapor production is at a minimum and therefore into the 

 polar regions and the colder parts of the temperature zone. This 

 would occur particularly where a cold and dry continental surface 

 tends to produce a strong outgoing radiation under a winter sky. 

 These conditions are found exactly in the northern plains in Euro- 

 pean Russia and in west Siberia. 



In the same year, 1880, Frederick Chambers investigated with the 

 aid of all available data the variations of the air pressure for the 

 period of years 1843 to 1879 in the tropical stations St. Helena, 

 Mauritius, Bombay, Madras, Calcutta, Batavia, and Zikawai, and 

 found an excellent agreement in the curves compared as regards 

 the march of the air pressure in these different stations. This was 

 of such a nature that variations in the westerly stations occurred 

 several months earlier than in the stations further east. Chambers 

 therefore assumed the existence of large atmospheric waves which 

 slowly and with varying velocity traversed the earth from west to 

 east like the cyclones in the ektropic regions. 



He compared these air pressure curves for the different stations 

 with the inverted sun spot curve and showed an excellent agree- 



