AMERICAN INSTITUTE. 401 



tingtiy obtained some striking experimental illustrations. (Annales de 

 Chemie, 3 series, toine i., p. 356, ct t. xi., p. 16). He has observed that 

 water may pass into the spheroidal ebullition at any temperature above 

 840*^, and remain in that state until the temperature falls to 28S'', when it 

 wets the surface and evaporates rapidly. Alcohol for this condition requires 

 273°, ether 142". A thermometer in water in the spheroidal state indi- 

 cates, 205-7''; in absolute alcohol, 167'9''; ether, 93-6°; hydrochloric 

 ether, 50'9°; sulphurous acid, 13"1'', which are all several degrees below 

 the ordinary temperature of ebullition of these liquids. Air is 815 times 

 lighter than water, and the range of the barometric pressure is equal to 

 one-tenth of the whole pressure, and affects the boiling point of water to 

 the extent of four and a half degrees ; for instance : when the barometer 

 indicates 27'74 inches, water boils at 208"; 28'84 inches, water boils at 

 210"; 29-92 inches, water boils at 212''; 30-60 inches, water boils at 

 213°— and on top of Mount Blanc, Saussure observed that water boiled at 

 184". It has further been observed that an elevation of 500 feet makes 

 one degree difference in the boiling point of water, and that liquids in 

 general boil in vacuo at from 67" to 145*^ less than under the ordinary 

 pressure of the air. The vessel, however in which the water is boiled 

 influences the boiling point to a considerable extent. Water in a glass 

 flask, having a thin film of shellac coating it, will not boil under 221" ; 

 and the action is impulsive, alternately rising and falling, as the thermo- 

 meter indicates a rise pr fall in the temperature. 



Prof. Hedrick was unable to see how barometric pressure could affect 

 the temperature at which water took up the spheroidal state. The water 

 simply evaporated as at ordinary temperatures, and the vapor given off at 

 low temperatures is identical with steam. It requires no removal of pres- 

 sure to generate it, as is seen by its filling a vacuum with steam at ordinary 

 temperatures. The action was between the hot air currents around the 

 water, and the vapor of the water, the hot dry air acting as a sponge to 

 absorb the vapor. 



Mr. Seeley considered that the barometric pressure, by reducing the 

 thickness of the film of steam, under the globule of water, brought the 

 water nearer to the heated metal, and thus allowed it to become warmer. 



Mr. Garvey stated that the elastic force of steam is always equal to the 

 pressure under which it is produced ; and, as it is also proportional to the 

 temperature of the water from which it is formed, it is obvious that to 

 generate a film of steam under a great pressure, requires more heat than 

 to generate it under a low pressure. 



Mr. Seeley considered this explanation as quite correct. 



Mr. Fisher said that many engineers attribute boiler explosions, in seve- 

 ral cases, to the change of water sviddenly from the spheroidal state into 

 steam, and instanced the boiler of the Great Britain as a case of defective 

 construction, in which the water spaces were so small that the water was 

 generally in a spheroidal state instead of being in contact with the tubes, 

 of which there are a great many employed, and the water spaces are con- 



