106 Dr. Pring on Etching by Electricity. 



101. Squalls may be the consequence of electrical reaction 

 between the terrestrial surface and oppositely excited masses 

 of air, and the intermixture of masses so excited in obedience 

 to the same cause, may be among the sources of rain, hail, 

 and gusts. The specific gravity of a body of air, electrified 

 differently from the surrounding medium, may be lessened 

 by what is called electric repulsion ; the particles inevitably 

 moving a greater distance from each other, as similarly elec- 

 trified pith-balls are known to do. 



102. Hence a cause of rarefaction, buoyancy, and conse- 

 quent upward motion, in a column of electrified air, more 

 competent than that suggested by Espy. 



103. Should it be verified that a gyration from right to left 

 takes place during convective discharges of electricity in hur- 

 ricanes, it may be referrible to the disposition which a positive 

 electrical discharge from the earth to the sky would have to 

 gyrate in that direction. 



I have prepared some strictures on Dove's Essay on the 

 Law of Storms, which will be the subject of a future communi- 

 cation. 



XVI. On a Method of Etching on Hardened Steel Plates 

 and other Polished Metallic Surfaces by means of Electricity. 

 By J. H. Pring, M.D. 



To the Editor of the Philosophical Magazine and Journal. 

 Sjr, 



1 HEREWITH transmit to you a rough specimen of what 

 I conceive to be a novel employment of the power of elec- 

 tricity, and shall be gratified should the process by which it 

 was effected prove susceptible of any useful application to the 

 arts. 



The method which I employed in the production of the 

 characters on the accompanying plate * was the following : — 

 Having six batteries of the kind invented by Mr. Smee, the 

 platinized silver plate of each being about three inches square, 

 I attached the steel plate to be etched upon to the zinc ex- 

 tremity of the batteries, a coil of covered wire, of considerable 

 length, being previously interposed between the steel plate 

 and the zinc: then taking the wire connected with the plati- 

 nized silver in my hand, I used it as an etching-tool on the 

 steel plate, — an electrical spark of great brilliancy, accom- 



* This was a steel plate, on which the words M Etched by means of 

 Electricity. Bath, 30th June 1843. I. H. P." together with some orna- 

 mental devices, had been produced by the above method. It gave only a 

 faint, just legible impression by the copper-plate press. — Edit. 



