PROGRESS OF METEOROLOGY IN 1889. 249 



places, and has investigated the variation both of the phases and of 

 the amplitudes of the single and double oscillations. The latter show a 

 remarkable independence of geographical and seasonal inHuences and 

 appear to be connected with a cosmical origin. The investigation also 

 shows that the amplitudes of the semi-diurnal oscillation decrease with 

 height in exact proportion to the pressure, and have a marked depend- 

 ence upon latitude. The yearly range exhibits two maxima at the equi- 

 noxes and also a third maxinuim which falls in January* in both liemi- 

 spheres, while over the whole globe the amplitude of the double daily 

 oscillation is smallest in July. [Nature^ xxxix, p. 517.) 



Mr. F. C. Bayard has reduced the hourly records of the barometer at 

 the nine observatories, in Great Britain and Ireland for the years 187G 

 to 1880, and has compared the resulting curves of diurnal range. 



The curves of inland places are smoother than those of sea-coast 

 stations, and the curves of i^laces to the westward are more irregular 

 than those of places to the eastward. In going toward the north the 

 diurnal range diminishes. {Nature, xxxix, ]). 023.) 



KraJ:atoa air leaves. — Part ii of the report of the Krakatoa com- 

 mittee of the Royal Society, has been prepared by General li. Strachey 

 and investigates the extraordinary air waves and sounds caused by the 

 Krakatoa eruption. Barometer traces from forty-seven stations scat- 

 tered over the whole world exhibit the passage of air waves travelling 

 around the world not less than seven times. The general velocity at 

 which the wave spread outward in concentric circles from Krakatoa as 

 a center was 700 miles per hour, which is slightly less than the velocity 

 of sound at zero Fahr., viz, 723 miles. A decided variation of velocity 

 was discovered in those portions of the wave which moved with or 

 against the earth's rotation, such variation being due to the prevalent 

 drift of the winds. 



In the extra tropics the wave moving from west to east was acceler- 

 ated, and that moving from east to west retarded, by about 1-4 miles 

 per hour; within the tropics the wave which passed through Mauritius 

 was affected in a reverse manner, the passage eastward being retarded, 

 while the westward was comparatively unaffected, the amount corre- 

 sponding to an east wind of about 10 miles per hour. These amounts 

 are almost precisely those given by Ferrel for the easterly and westerly 

 components of the prevailing currents at their respective latitudes. 



The area over which the sound of the eruption was heard is estimated 

 at one-thirteenth of the entire earth's surface. {Fature, xxxix, p. 566.) 



A curious sudden barometric oscillation passed over central Euroi)e 

 on the evening of January 31, 1889. Dr. E. Herrmann, of the Deutsclie 

 Seewarte, traces it from Kertum (latitude o4:0 54'), where it occurred at 

 7'' 50'" p. M., Berlin time, to Pola (latitude 49° 42'), which it reached 

 at 4^ 38"' A. M., on February 1, having travelled at the rapid rate of 

 about 71 miles an hour. The cause of the phenomenon is unexplained. 



