STEAM. 85 



ebullition ; while on the other hand, boiling water, 

 or the application of flame, will cause the boiling to 

 cease. 



202. EXPLANATION. The principle is 

 e^ tne same as m tne experiment of the last 



the culinary paragraph. As the steam condenses, by 



paradox. r . . . J 



the cooling influence of the air, a partial 

 vacuum is produced, and a diminished pressure, which 

 enables the water to boil with less heat. Cold water, 

 by condensing the steam and removing the pressure 

 more perfectly, increases the ebullition, while boiling 

 water or flame renews the steam, and consequent pres- 

 sure, and therefore checks boiling. 



203. WATER HAMMER. The test-tube 

 " Water Ham- prepared as above, is a simple form of the 



" water hammer." If very thoroughly 

 cooled, and then sjiaken with the kind of motion which 

 would be required to make a bullet rise half way in 

 the tube and fall again, the water will strike like lead 

 on the bottom. It is because there is no air and but 

 little vapor present to break its fall. 



204. SUGAR BOILING. When syrup 



Now may sy- .,.,,, , ,. 



rup be boiled is boiled down under the ordinary pres- 



z. gure Q f tne atmosphere, it is apt to be 

 browned or injured in flavor. By boiling it in a pan 

 with an air-tight lid, and pumping off the air, and the 

 vapor as fast as formed, boiling may be easily effected 

 at a temperature as low as 150. This method is put 

 in practice by sugar boilers, and the disadvantages above 

 mentioned are thus avoided. 



