PROGRESS OF METEOROLOCJY IN 1889. 255 



nioviug destructively onward in slightly diverging»straiglit Hues, in 

 Iowa generally towards the southeast. The barometer rises suddenly 

 and the thermometer falls greatly under the blow of this cold air of 

 the upper strata suddenly striliiug the ground. While occurring occa- 

 sionally in the spring and early summer, the derecho has its period of 

 greatest frequency and intensity in the 'midsummer months, July and 

 August. In these two months the tornado does not occur in Iowa. 

 The writer shows that the list of Iowa tornadoes published by Lieu- 

 tenant Finley is untrustworthy, and then gives a corrected list of all 

 the authentic tornadoes that can be verified by reports. These have 

 occurred in April, May, June, and October. {Am. Meteor. Journal, v, 

 p. 385.) 



Water-spouts. — Mr. S. R. Elson Reports several water-spouts observed 

 on the Hooghly. One was seen " projected from the level vapor-plane 

 of a towering cumulus cloud ; through a telescope it showed well the 

 downrush on the inside of the tube, and its counterpart the whirling 

 uprush on the outside, twisting and coiling round and round against 

 the watch hands (face upwards). In another case after a water-spout 

 had been observed for some time and it was beginning to shrink and to 

 draw itself uj)wards, "the inside downrush was again seen to advan- 

 tage and the simultaneous upward whirl around the dense remains of 

 the tube, which I can not do better than liken to the turning inside 

 out of a coat-sleeve, only the end of the tube was always ragged ; and 

 here, where the reversing process was taking place, there was great 

 commotion in the air currents. 1 had a good telescope, observed these 

 phenomena very carefully, and was on the alert for optical illusions." 

 [Nature, xxxix, p. 334.) 



Rain-fall and cyclones.— The Report on the Meteorology of India in 

 1887 (Calcutta, 1889) calls attention to the relation that has previously 

 been shown to obtain between rain-fall and cyclones during the south- 

 west monsoon period. There is a very marked tendency for cyclonic 

 rain-storms to run along the trough of low pressure, the mean position 

 of which during the rains stretches from Sind or Cutch in an east south- 

 east direction to the eastern districts of the central provinces, Orissa and 

 Chutia Nagpur. An examination of the storm tracks of 1887 and 1888 

 has shown that the great majority of these storms marched across the 

 coast in the direction of the belt of lowest pressure at the time of their 

 formation, and hence it nmy be inferred that if a depression forms dur- 

 ing the rains in tlie bay it will ver^^ probably run along the belt of 

 lowest pressure or the trough of minimum pressure in existence imme- 

 diately antecedent to its formation. Since the chief characteristic of 

 such a barometric depression is light and variable winds, it will be seen 

 that this principle virtually coincides with the rule that cyclonic storms 

 in the bay march in the direction of least relative air motion immedi- 

 ately antecedent to the formation of the cyclone, which is a more gen- 

 eral rule than the former. 



