256 THE STORM OF SEPTEMBER 21, 1868. 



axis O causes it to revolve, and with it the larger pulley which 

 imparts a more or less magnified motion to the pencil. 



The lever carrying the rod J does not move unless the test piece 

 slips in the clips, in which case the arrangement of the wire over 

 the pulleys K and Q, ensures that this movement will not be 

 recorded as an elongation. The bent springs keep the points 

 always in contact with the test piece. All the pulleys revolve 

 upon conical centres. 



Plate 4 shows a series of diagrams obtained from New South 

 Wales Timbers tested as beams on supports 4 feet apart. The 

 beams were 6 inches wide by 4 inches deep. The apparatus has been 

 used for recording in a similar manner the results of testing rolled 

 girders, built beams, angle and Tee-irons, bulb-irons, rails, also for 

 recording the results in a similar manner of compression and 

 tensile tests of iron and steel, timber, brass, bronze, <fcc 



The apparatus was designed by J. A. McDonald, M. Inst. C.E. 

 and the author, and made in the author's laboratory. 



THE STORM OF 21st SEPTEMBER, 1888. 



By H. C. Russell, B.A., F.R.S., &c. 



[One Diagram.] 



[Read before the Royal Society of N.S.W., October 3, 1888.'] 



The thunderstorm on the afternoon of Friday, 21st September, 

 1888, presented some features which are worthy of being placed 

 on record. For two days before the barographs in South-Eastern 

 Australia indicated that general uneasiness in the atmosphere 

 which is characteristic of thunderstorm periods. That the whole 

 system was moving eastward is shewn not only by the earlier 

 indications in the Adelaide barogram, but also in the weather 

 maps for those days. On Thursday rain fell at many places, 

 and thunderstorms were reported in some places. On Friday 

 thunderstorms occurred at many places. At Adelaide a heavy 

 thunderstorm and sudden rise in the barometer began at 6 p.m. ; 

 at Melbourne on the same day the barometer fell 0.100 between 

 1 and 1.50 p.m. In New South Wales thunderstorms occurred 

 in many places, and it was evident that the conditions giving 

 rise to them were increasing in intensity. At Sydney at 4.30 p.m. 

 we had the remarkable storm to which I shall refer more in detail 

 presently, and on Saturday violent storms were general over 



