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ON ELECTRICAL OBSERVATIONS AT KEW. 193 
minutes. - It is also to be remarked, that at the commencement and termi- 
nation of the second, oscillations in the kind of tension occurred, the tension 
at the occurrence of the first flash being positive 60° of Henley, and that 
at the last also positive 50° of Henley: the intermediate tensions were negative. 
Oscillations also occurred during the periods of heavy rain. 
At Greenwich the same storm was observed, the clouds recorded being 
cirro-stratus and scud. It appears to have commenced at 5" 49™ p.M., at 
least so far as the affection of the instruments is concerned; the record is as 
follows :—[“ This storm first rose in the N.W.; it then passed round to the 
north, and afterwards to the east, as also did the wind; at 5" 50™ there was 
a vivid flash of lightning, followed by thunder at the interval of seven 
seconds; at 54 55™ there was another very bright flash, and thunder followed 
at an interval of two seconds ; this was a long peal, the crackling continuing 
from 45° to 59%. Several flashes of lightning took place between 6" and 
65 15™, followed by thunder at intervals of one, two and three seconds. 
Between 62 and 62 20", 0°78 inch of rain fell at Mr. Glaisher’s residence ; 
-after this time the lightning ceased ; the rain however continued, but not so 
heavily.” —G. ] 
From this record it may be gathered that the first flash of lightning oc- 
curred at 5" 50™ p.m., being six minutes earlier than the occurrence of the 
first flash at Kew; it is described as very vivid, and followed by thunder at 
the interval of seven seconds. The second flash, which was very bright, 
occurred at 5" 55™ p.m., one minute earlier than the first at Kew; it was 
evidently much nearer than the first observed at Greenwich, the interval 
being two seconds. Between 62 and 6" 15™ p.m. several flashes are recorded, 
the point of discharge being upon the whole nearest to the observatory 
during this quarter of an hour. During the same period six flashes were 
registered at Kew, from four of which sparks were obtained, the longest 
being 0-4 inch ; it occurred at 6" 5™ p.m. This quarter of an hour was evi- 
dently the period in which the focus of the storm passed both observatories, 
and during the twenty minutes between 6? and 6" 20™ Mr. Glaisher registered 
0°78 inch of rain at Blackheath. It is this circumstance to which we wish 
to refer in connexion with the azis of the storm, it being evidently accom- 
panied at Blackheath by a great precipitation of rain. Less rain appears to 
have fallen at Greenwich, about half an inch having been registered during 
the twenty-four hours from 95 20™ a.m. of July 1 to 9" 20™ a.m. of July 2. 
During the storm changes of tension occurred, the maximum tension being 30° 
of Henley and the longest spark 0:23 inch. 
(°) July 5, 1844.—Between 11" 18™ a.m. and 1" 15™p.m. a thunder-shower 
passed over the observatory at Greenwich. Positive and negative electricity 
were exhibited ; heavy cumulo-strati covered the sky until 11" 55" a.m., when 
heavy rain began to fall and thunder was heard in the N.W.; max. tension 
10° of Henley ; sparks max. length 0°13 inch. During this time the weather 
at Kew is registered “fine but cloudy,” but at 1" to 1> 5™ p.m. a heavy 
shower of rain is recorded, which does not appear materially to have affected 
-the instruments. 
Between 4" 0™ p.m. and 45 46™ p.m. changes are again recorded at Green- 
wich with rain falling; the electricity was negative until 4" 12™ p.m., when 
itsuddenly became positive, max. tension observed 120 div. Volta (2). Du- 
ring the whole of this time the charge was negative at Kew. 
 (®) August 8, 1844.—There can be but little doubt that the fine rain at a 
distance observed at Kew at 1" 26™ p.m. is the same shower that fell at 
Greenwich at 1 35™ p.m.; the only link in the chain of evidence required to 
identify it is the direction in which the fine rain was seen from Kew; both 
1849. oO 

