78 ANNUAL OF SCIENTIFIC DISCOVERY. 



results said to be secured are cheapness of distillation, perfection in 

 the operation, saving annually for France alone an amount of the 

 metal estimated at two hundred and forty thousand pounds ; and, last- 

 ly, and this is the most important consideration, the rendering 

 absolutely innocuous an occupation which proves inevitably and speedily 

 fatal to all who continue steadily employed in it. The distillation of 

 mercury is henceforth as harmless as the distillation of water. Paris 

 Correspondent of National Intelligencer. 



IMPROVEMENT IN THE MANUFACTURE OF WHITE-LEAD. 



THE London Mechanics'' Magazine says, that Mr. J. E. D. Rogers 

 has recently taken out a patent for an improved method of manufac- 

 turing white-lead. He proposes to manufacture it by suspending 

 pieces of sheet or cast lead, bent in the form of two sides of a triangle, 

 upon frames erected in a room or chamber which is capable of being 

 darkened and rendered air-tight, or nearly so, when required. Under- 

 neath the frames are troughs, some of which are filled with a fluid 

 capable of passing into the state of vinous fermentation spontaneously, 

 or of doing so on the addition of yeast, and thereby evolving carbonic 

 acid gas. The other troughs contain sour beer, vinegar, or other 

 similar fluids, into which steam-pipes from a boiler are caused to 

 open, so as to produce acetic acid, or pyroligneous acid and aqueous 

 vapors. The modus operandi is as follows : The pieces of lead are 

 suspended in the frames, as close together as possible, without actual 

 contact, and the chambers made air-tight, and maintained at a temper- 

 ature of from 70 to 80 F. As soon as the carbonic acid gas is 

 evolved, the chamber is darkened, and steam admitted about three 

 times in every twenty-four hours. The chamber is provided with a 

 man-hole, to allow, of the troughs being replenished when the fluid 

 contents have been exhausted, which will occur at the expiration of 

 forty-eight hours. This operation for converting metallic lead into 

 carbonate of lead generally takes twelve days. 



AMERICAN SALT. 



FROM the report of a committee to the New York Legislature, 

 April, 1850, we derive the following facts. 



About one third part of all the salt manufactured in the United 

 States is made at the Onondaga salt springs, and nearly one fourth of 

 what is consumed in the Union comes from the same source. Under 

 the fostering care of the State, the quantity manufactured has con- 

 stantly increased from year to year, until, as stated by the superintend- 

 ent, the number of bushels in 1849 exceeded five millions, requiring 

 the daily consumption of one thousand cords of wood, and the daily 

 use of eight thousand barrels during the manufacturing season, and 

 furnishing employment in the various departments connected with the 

 interest of more than five thousand men. For a series of years the 

 State derived considerable revenue by tax upon the whole amount of 

 salt manufactured ; but of late this policy has been to a great extent 



