Formation and Dispersion of a Thunder Shower. 59 



Art. IX. — Formation and dispersion of a Thunder Shower — 

 Parhelia, and Meteorological Register ; by Willis Gatlord. 



To THE Editors. — GentleQnen, — In looking over my meteor- 

 ological notes for 1839, under date of August 31st 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 S. 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 21st. A 

 little after 2 o'clock on the 21st I observed a large mass of cu- 

 mulus in the S. 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 S., but between the two there W'as 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. There was no perceptible wind from any 

 quarter. 



I was in my garden some ten or twenty minutes after making 

 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 could 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 in a 

 few minutes the stratus began to form rapidly at the base of the 



