Formation and Dispersion of @ Thunder Shower. 59 
Art. 1X. —Formation and dispersion of a Thunder Shower— 
Parhelia, and Meteorological Register ; by Witi1s GayLorp. 
To rue Eprrors.—Gentlemen,—In looking over my meteor- 
ological notes for 1839, under date of August 21st I observed the 
following :—‘‘ Witnessed the formation and dispersion of a thun- 
der shower, attended with some remarkable phenomena ;’’ and as 
the formation and action of clouds and storms is always an ob- 
ject of interest, I have thought a description of the one alluded 
to might not be altogether without its claims to notice. 
The wind on the 21st and for two days previous had been 
southwardly, most of the time 8. E. ‘The 20th was one of the 
warmest days of the season, the thermometer at 2 o’clock being 
at 90°, and on the 21st the mercury at 9 o’clock was 73°, and at 
2 o’clock at 80°. Although the lower current of air was south, 
the upper did not seem to follow the same course, but was more 
from S. of W. This was shown by the course of some electric 
clouds on the 20th, and of one on the forenoon of the 2Ist. A 
little after 2 o’clock on the 21st I observed a large mass of cu- 
mulus in the 8. E., not at a great distance, and with little appa- 
rent elevation. An electric cloud which was passing lay low in 
the horizon at the 8., but between the two there was no connec- 
tion ; the mass of cumulus was completely isolated, a line of blue 
sky being distinctly visible between the two; nor was there any 
appearance of stratus, or the cirri, which invariably accompanies 
an electric cloud. Laie was no perceptible wind ices — 
quarter. | 
T waite sipcepidebanine an an: ‘easy innlenaivas galing 
the above observations, and not far from 3 o’clock, when my at- 
tention was arrested by a heavy roaring in the direction of the 
cloud, like that which accompanies a fall of hail or violent wind, 
and looking at the cloud, I perceived that a mass of cirri was 
streaming from the summit of the mass, and stretching upwards 
and N. E. from its highest point. There was little appearance of 
stratus at this time, and not the slightest indication eould be dis- 
covered that rain or hail was falling from the cloud. I carefully 
examined the cloud to detect any motion which might exist in 
it, but not the least movement was perceptible, except that ina 
few minutes the stratus began to form rapidly at the base of the 
