L. MECHANICS AND ENGINEERING. 437 



washings in hot water have proved to have no effect upon it. 

 It can also be used as a thickening in calico-printing. Several 

 of the technological journals speak of this substance as a very- 

 important addition to the resources of the dyer and manu- 

 facturer. Care must be taken to retain it in air-tight vessels 

 until it is used, as it is not easily rendered soluble again when 

 it has once become hard. 18 Jt, XXL, 29. 



MINERAL PRODTJCTS OF EUROPE FOR 1874. 



The Austrian statistician Brachelli estimates the total 

 mineral product of all the countries of Europe for 1874 to 

 have been as follows : Platinum, 1025 kilogrammes ; gold, 

 6900 kilogrammes ; silver, 300,000 kilogrammes ; pig-iron, 

 240,000,000 hundred-weight; copper, 600,000 hundred- weight ; 

 lead, 5,300,000 hundred-weight; zinc, 2,700,000 to 3,000,000 

 Imndred-weight ; tin, 205,000 hundred-weight; coal, 4,376,- 

 000,000 hundred-weight ; salt, 95,000,000 to 100,000,000 hun- 

 dred-weight; manganese, 1,616,000 hundred-Aveight; antimo- 

 ny, 5700 hundred-weight. 



PRESSURE GAUGE TO REGISTER 54,000 POUNDS. 



A mechanical novelty worthy of being placed on record 

 is a mercury column pressure gauge lately completed by 

 Thomas Shaw, of Philadelphia, for a company in that city, 

 which is capable of registering a pressure of 54,000 pounds 

 to the square inch. The body of this gauge was forged solid 

 from the best Midvale steel, and bored and turned to the 

 proper shape. The total height is six feet, that of the mer- 

 cury column being four and a half feet. The area of the 

 large plunger is six and a half inches, and of the small one 

 three sixteenths, and the movement about one thousandth of 

 an inch. No gauge has yet been built to register so high a 

 range of pressure as this one. 18 A, XXL, 35. 



INCRUSTATION OF BOILERS. 



At One of the recent meetings of the French Academy, 

 this important subject was discussed. M. Lesueur, a tele- 

 graph inspector, sent a communication to the Academy set- 

 ting forth the efficacy of zinc in protecting steam-boilers 

 from incrustation. The substance of M. Lesueur's remarks 

 was to the effect that in many instances the action of zinc 



