as observed at the Kew Observatory. 421 



very considerable portion of the sky from the zenith to the 

 eastern horizon, the cloud, apparently a sheet of cirrostratus, 

 presented a most remarkable reddish hue. Cirrostratus had 

 been prevalent during the day. At 9 a.m. I registered cin'us, 

 cirrostratus, cirrocumiihis and cumulus', and at 3 p.m. cirro- 

 stratus and cumulus. On both occasions these clouds were 

 moving from the south-west. At 3 p.m. I observed a very 

 splendid solar halo ; the portion of it not covered by cumuloid 

 clouds was exceedingly well-defined, the angular distance 

 between its upper portion and the sun being 21° 49'. It con- 

 tinued more or less visible until 4 p.m., and presented an ellip- 

 tical form, the lower portion being much further from the sun 

 than the upper. The interior boundary of the halo exhibited 

 a reddish-brown tint, gradually passing towards the exterior 

 boundary into a softened white, which thinned off into the 

 general mass of cloud ; the darkness of the interior space, espe- 

 cially near the halo, was very striking. When I first noticed 

 the threatening aspect of the clouds, those in the immediate 

 neighbourhood of the observatory were moving from the 

 S.W. At 5^1 40™ P.M. a few large drops of rain fell ; they 

 were almost immediately succeeded by hail (small), and hail 

 mingled with heavy rain continued to fall until 6^ 10™. Du- 

 ring this time the process of nimbification proceeded rapidly, 

 extending from the N.E. toisaards the S. W. ; so that although 

 just previous to the commencement of the storm the clouds were 

 moving in the opposite directioriy the action, now very consider- 

 able, rapidly cofiverted the cumuli hovering over the observatory, 

 and more 'probably to some distance S. fV. of it, into nimbi, ac- 

 companied with a very copioxis precipitation of hail. While this 

 active precipitation of hail was proceeding, the electrical con- 

 ductor became charged to about 40° of Henley's electrometer, 

 the pendulum vibrating rapidly at the time when the hail came 

 down in greatest abundance and of the largest size, and sparks 

 were observed 0*3 inch in length. 



" The heavy rain previously noticed ceased at 6^ 27™, and 

 during the 47 minutes of this portion of the storm the tempe- 

 rature declined 4°'7. After this a lighter rain fell until 7'' 10™, 

 in the course of which the tension, as manifested by the con- 

 ductor, increased : the vibrations of the pendulum of Henley's 

 electrometer also increased ; on one occasion it reached 90°, 

 with sparks 0*70 inch in length. During the storm the charge 

 was generally negative." 



We have in the above phaenomeha an illustration of Mr. 

 Howard's remark (see vol. xxxvi. p. 167): — "This rain 

 opens an immediate communication with the earth ; the po- 

 sitive electricity, which before rendered the particles buoyant, 



