258 THE STORM OF SEPTEMBER 21, 1888. 



the ordinary Richard recording aneroid, shews the same sudden 

 change ; second, one of the most perfect and largest sized Redier 

 barographs, a kind which is acknowledged to be the most perfect 

 instrument for recording barometer changes made in Europe, 

 shews the same curve ; and third, a new form of recording 

 barometer which I have had made, and which is the most 

 sensitive of the lot, also shews the same curve. In passing it 

 may be mentioned that the Sydney barograph and the recording 

 aneroid both shew the whole change to have amounted to 0.060, 

 while the Redier shews only 0.040, the reason for which is no 

 doubt that the Redier from the method of recording, was not 

 capable of shewing the whole of such a sudden change. After 

 this extraordinary fall and rise, the barometer fell slowly for 

 20 minutes as the storm passed away. Scarcely any effect was 

 produced by the storm on the day's barometric curve, there is 

 just the disturbance lasting half-an-hour, before and after which 

 the diurnal curve is undisturbed. See photolithograph of this day's 

 record attached. 



At the height of this storm its aspect was very grand, — the 

 thunder, lightning, rain, and wind, the latter sufficient to drive 

 the rain quite horizontally over the hill, were truly grand, but 

 all over in ten minutes, and the height of it in five minutes. 

 Just at the moment of extreme barometric depression something, 

 probably a thunderclap, shook the Observatory sufficiently to 

 bring the seismoscope of the seismograph made by the Scientific 

 Instrument Company of Cambridge into action. An electric 

 •contact was made duly recording the exact instant, and setting 

 all the recording parts in motion. The rain fell for a few 

 moments as shewn by the record at the rate of four inches per 

 hour, but it is probable that this is too little, because the wind 

 was so violent that as mentioned before the rain was driven 

 horizontally, and did not seem to fall at all in the strongest gusts. 

 All fell in ten minutes, and the amount was 0.56in. 



We have recording barographs at Sydney, Penrith, Dubbo, 

 Bourke, Wilcannia, Hay, Albury, and Lake George, and of course 

 at Melbourne and Adelaide, and none of these shew any change 

 resembling that at Sydney ; and all the reports that have come 

 in seem to indicate that the storm was quite local, — one of those 

 small but intense cyclonic storms which occur from time to time, 

 and after travelling for a few miles die out. When first seen 

 from the Observatory it was south-west by west, and came 

 steadily on from that direction, and passed to north-east on the 

 west side of the Observatory, as shewn by the change of wind 

 and actual observation ; at Homebush and other points the hail 

 was very heavy, but at Sydney Observatory only a few hailstones 

 fell, they were rounded and the largest elongated, none so much 

 as half-an-inch in length. 



