192 REPORT—1849. 
(d) This flash appeared to have no effect on the electrometer. : 
(e) The “ gush of rain” arrived at the observatory. It may be remarked 
that after this, thunder was heard but once, and in all the records it is de- 
scribed as distant. From the time thunder was last heard, 42 21™ p.m., the 
charge had gradually fallen to Volta 10 div. P. The highest tensions were ob- 
served, not when the rain was heaviest, but when the discharges (at a distance) 
took place more frequently. It is probable that after the cessation of these 
discharges the “ gush of rain” came travelling on, being still accompanied by 
the causes of its production, and a corresponding oscillation of the tension 
occurred. 
(f) The increase of tension on the occurrence of the discharge is very 
apparent, as well as the gradual decline afterwards, notwithstanding the ces- 
sation of rain which occurred within the next 11 minutes. 
(") July 1, 1844.—As the records of this storm have already appeared 
in the volume of Reports for 1844, page 134, we shall not further introduce 
them to the reader. On a careful consideration of the record it will be found 
that the storm may very naturally be divided into three sections, viz. the 
period of heavy rain previous to the electrical discharges; the period of the 
discharges themselves ; and the period of rain succeeding the discharges, a 
portion of which was heavy. ‘he times are as follows :—first period 5" 30™ 
P.M. to 54 55™ p.m. inclusive=25 minutes ; second period 55 56™ p.m. to 
65 24™ p.m. inclusive—2Z9 minutes; third period 62 25™ p.m. to 74 50™ P.M. 
inclusive=1 hour 26 minutes. We have in the first period a decided instance 
of heavy rain, characterized on one occasion as very heavy, being in advance of 
the actual thunder-storm. During the second period neither ¢hunder nor heavy 
rain, except on one occasion, appear to have been noted: it is however to be 
presumed, as we shall have occasion hereafter to notice, that from the fre- 
guency and character of the flashes they were accompanied by both, and the 
probability is, that during the exhibition of the lightning the rain that fell 
was much heavier than that in either the preceding or succeeding period. 
In the third period the heavy rain continued about half an hour. The values 
of the tensions having reference to these periods are interesting. ‘The mean 
of the tensions recorded during the first, without having regard to kind, is 
32° of Henley; that of the second 48° of Henley ; and that of the third 27° 
of Henley, or during the heavy rain only, 33° of Henley. The connexion 
between the high tensions and the electrical discharges from the cloud is 
very apparent; also the mean values of the tensions during each period of 
' the heavy rain indicate a certain relation between them. The entire phe- 
nomena strongly suggest the existence of an axis characterized by the active 
development of strong electric action ; the tension of the cloud and probably 
that of the rain being so enormous that frequent discharges took place to 
restore the equilibrium. This axis occupied about half an hour in passing 
the observatory. It is probable the strong action going on in the centre 
was communicated to a zone of nearly the same breadth in all its parts, in 
which the principal phenomenon was ¢he rapid formation of rain unaccom- 
panied by electric discharges. In connexion with this it may be remarked 
that the third period may be subdivided into two, the first characterized by 
heavy and the last by light rain; the duration of the first was, as we have 
already noticed, 30 minutes, namely from 6" 25™ p.m. to 65 55™ p.m. inclusive, 
and this may probably be regarded as the true termination of the storm. 
The three periods,—viz. preceding heavy rain; actual thunder-storm; and 
succeeding heavy rain—do not differ very considerably in duration from each 
other. The first = 25 minutes, the second =29 minutes, and the third = 30 

