146 On Bust Whirlwinds and Cyclones. [No. 2. 



clouded state of the atmosphere, occasional glimpses only of the upper 

 cloud strata can be caught ; and the difficulty becomes an impossibility 

 at sea, from the motion of the vessel: accordingly, these distant 

 clouds, appear under such circumstances, to be stationary, and are 

 often so reported. 



Notes. 



1. — The following account by Captain Gastrell of the effects pro- 

 duced upon an Electro-magnetic battery in action during the passage 

 of a Dust-Storm, will be read with interest. 



" I have the pleasure to send you a Memo, of the phenomenon I 

 mentioned to you as observed by me at Cawnpore, with the Electro- 

 magnetic machine during the passage of a Dust-Storm. 



"In the hot weather of 1847, 1 was experimenting one day at about 

 11 a. m. with an Electro-magnetic machine. It was of small size, 

 — the wire coil about 200 yards in length and fine, — the battery I 

 was using to impel the magnet in the break cup, was one of 1 2 or 1 6 

 pairs of zinc and copper plates ; each plate about 4 inches square, and 

 was charged with dilute sulphuric acid and water. Shortly after the 

 battery and magnet were in action, and sparks passing freely, a dust- 

 storm came up from the West, passing directly over the house I was in 

 towards the N. E. or E. N. E. 



" On its approach, I observed the action of the magnet decrease 

 gradually, until, in the dead lull or calm that usually precedes such 

 storms, it ceased revolving. 



" The action of the battery during the same period increased in 

 intensity and apparently in proportion to the decreased revolutions of 

 the magnet. 



" It was at its maximum of intensity about the time the centre of the 

 storm was passing, and, supposing the stoppage of the magnet might be 

 owing to too much energy in the battery, I disconnected the coil, and 

 placed it in connection with a single cell battery with platina plates. 



" This I charged with a solution of sulphuric acid and water, decreas- 

 ing the strength of the solution with more water from time to time, 

 but with no effect on the magnet. I then emptied the cell, and charg- 

 ed it with a solution of common salt and water, with the same want of 

 success : I then removed the single cell battery, and re-connected the 

 coil with the 12 plate battery, and left it. 



" No sooner had the storm of dust passed, and light rain began to 



