164 Transactions of the South African Philosoi^hical Society, 



We have here, apparently, a confirmation of Hann's contention that 

 the barometric oscillations belong more to the upper than to the 

 lower reaches of the air. For if they belonged below, the air current 

 would be setting inwards at IX. instead of outwards. 



The barometric characteristics of this air current become plainer if 

 we separate it out into its harmonic constituents. Its second ampli- 

 tude is relatively large compared with the first. Its respective 

 epochs fall approximately :— 



Vi an hour and three-quarters later, 



V2 an hour later, ~" 



V. an hour earlier, and 



V4 an hour and three-quarters later 



than those of pressure. It is curious that the earlier phase of the 

 third periodic term should be accompanied by an amplitude so 

 modest. Curious too that the phase should be almost exactly that of 

 the cloud term for Trevanarum. 



It seems not improbable that the fact of the variation in the 

 quantity of air over each meridian, due to the east component of 

 wind-velocity, may prove of considerable moment in the hands 

 of the physicist. I have not seen it referred to before, and indeed it 

 is not likely to have been easily detected at any place having a less 

 favourable geographical position than Kimberley has.''' 



* [It is interesting to compare this result with that discovered by Hann, and 

 described by him in a paper read on Dec. 11, 1902, before the Academy of Sciences 

 in Vienna, on the daily rotation of the mean wind-direction, and on an oscillation 

 of the atmosphere, of semidiurnal period, over mountain-peaks of altitudes lying 

 between 6,500 and 13,000 feet, a " Sonderabdruck " of which has recently been 

 published: — "Das wichtigste Ergebnis ist, dass bei alien vier Componenten, 

 namentlich aber bei der N- und S-Componente, eine grosze halbtagige Periode 

 vorhanden ist, welche der ganztagigen gieichkommt oder sie selbst an Grosze 

 iibertrifft. . . . Die Constanz der Phasenzeiten und die Grosze der halbtagigen 

 Peroide macht es wahrscheinlich, dass diese regelmaszige tagiiche Oscillation 

 der Luftmassen in 2 bis 4 km Seehohe mit der regelmiiszigen tiigiichen Barometer- 

 schwankung in Beziehung stehe." (Feb. , 1903).] 



ERRATA IN VOL. XI., PART 4. 



Page 244, last line, and third line from the bottom ; also page 245, second and 

 fifth lines, /or " temperature of the day " read " temperature of the month." 

 Page 203, twenty-lifth line, /or "present volumes " read " annual volumes." 



