Scientific Intelligence. 195 



an aperture at the top into which the molten lead is poured. The 

 clay is then taken off and the lead driven home with a blunt chisel 

 and hammer. It was in driving home the lead that the shocks were 

 produced. The sun was nearly vertical, and the thermometer at 

 93° ; the ditch somewhat damp, and the pipes warm from the ac- 

 tion of the sun upon them. The principle is no doubt that of gal- 

 vanism, but as the cause is supposed to be entirely new, the plumber, 

 (Mr. Johnson, from Philadelphia,) having never known any thing 

 like it during his long experience in that city, we should be glad to 

 receive the opinion of scientific men upon it. 



We have since been informed, that after a heavy rain on the ensuing 

 day, and the covering of a few feet of the pipes some distance above 

 with earth, the phenomenon did not occur, nor has it since occurred. 



Remarks by a correspondent. — The phenomenon belongs, without 

 doubt, to thermo-electricity. The exciting agent in the voltaic series, 

 (for the chain of pipes with interposed lead soldering, may surely be 

 considered as such a series,) was made active by the intense heat of 

 the sun. The pipes being of a black color, probably acquired a tem- 

 perature much above that of the surrounding air ; they were probably 

 also unequally acted on in consequence of their lying in a ditch. 

 «■ * rr * * 



We agree entirely in opinion with our correspondent, and cannot 

 doubt that much of terrestrial and atmospheric electricity arises from 

 similar natural galvano-electric combinations existing in the various 

 arrangements of matter. — Ed. 



3. Test for lead in oil of Vitriol, by A. A. Hayes. — Commer- 

 cial oil of vitriol often contains much sulphate of lead, to detect which 

 and separate it in part, a few drops of strong muriatic acid may be 

 dropped into the cold acid, an opaline, or milky appearance, indi- 

 cates the presence of a minute portion only ; if considerably con- 

 taminated, a precipitate falls, from which the clear acid may be de- 

 canted. This effect seems to depend on the insolubility of chloride 

 of lead in cold sulphuric acid ; when heated, the acid dissolves it. 

 Muriatic acid in water, readily dissolves and decomposes sulphate of 

 lead ; the solution containing free sulphuric acid, may be boiled a 

 long time without decomposition. By evaporating the liquor and 

 heating the salt, decomposition of the chloride is effected. Com- 

 mercial oil of vitriol dissolves much more sulphate of lead, than con- 

 centrated sulphuric acid does j the result of one experiment gave 



