ON RADIOTELEGRAPHIC INVESTIGATIONS. 41 



the Gulf of Bothnia. The worst X stonn in the American records was 

 also accompanied by the exceptionally rapid movement eastward from 

 the Pacific of a cyclonic depression with steep pressure gradients. A 

 report from a Califomian station of the Marconi Wireless Telegraph 

 Company of America on this latter occasion states that the barometer 

 was fluctuating between 29-44 and 29-52 inches very rapidly, the varia- 

 tions being accompanied by gusts of wind which attained the velocity of 

 70 miles per hour. The disturbance produced in the telephones by the 

 strays amounted to a roar. On this occasion, between 1 p.m. and night, 

 the strays rapidly diminished as the wind fell and the barometer rose. 

 These meteorological conditions are precisely those that accompany or 

 precede thunder storms and line squalls; and, in fact, the records 

 of the Meteorological Offices, and of the observers reporting to the Com- 

 mittee, all lead to the conclusion that X storms are often associated 

 with thunder storms at places not very far distant. Sometimes all the 

 symptoms of thunder weather except thunder and lightning may.be 

 present in a locality and a heavy X storm be recorded : e.g., Mr. P. H. 

 Burns, Superintendent of Telegraphs in the Bahamas, reports thathe 

 has often been experiencing an X storm when a sudden shift of wind 

 to the north-west (wind velocity about twenty miles per hour) has taken 

 place, and been followed by heavy rain, a calm, low temperature, 

 lessened humidity, and a total disappearance of strays — all without 

 thunder or lightning. To some extent these are symptoms of the 

 passage of a small secondary or V depression such as might not be 

 recorded on synoptic charts. 



It is well known that the unstable atmospheric conditions bringing 

 thunder weather sometimes move at a relatively slow rate from place 

 to place, and may have their movements traced by the ordinary 

 methods of meteorology. The analysis of the radiotelegraphic records 

 shows that such convective weather can be anticipated several days in 

 advance. This is particularly well borne out by some of the Malta 

 records when taken together with some abstracts of the meteorological 

 conditions kindly supphed by Dr. T. Agius, in charge of the Observatory 

 at Valetta: — 



Strays bad All Aug. 22 and 23, 1914 . Greatest rainfall of month Aug. 24. 

 „ „ Nights of Sept. 22 and 23 



and day of 24 . . „ » ,, Sept. 25. 



„ „ All Oct. 6 and 7 . . „ „ „ Oct. 9. 



„ „ All day Nov. 12 . . „ „ „ Nov. 13. 



Dec. 26 and 27 . . . Greatest fall in temperature, lowest 



barometer Dec. 28. 

 ,, „ Jan. 20, 1915 . . . Greatest rainfall Jan. 21. 



„ „ May 27 and 28, 1915. . „ „ May 31. 



A report received from the wireless-telegraph station of the Govern- 

 ment of Australia situated at Esperance states that during the day-time 

 rain is preceded in at least eighty per cent, of cases by interaiittent 

 disturbances. Strays of varying strengths may be heard from 6 a.m. to 



