466 ANNUAL KECORD OF SCIENCE AND INDUSTKY. 



gree the power of extinguishing the flame of certain highly- 

 combustible substances, and especially that of burning pe- 

 troleum. By pouring a small quantity of this substance 

 upon such a burning mass of oil, it is affirmed that the flame 

 will be at once extinguished, and that, furthermore, a small 

 quantity added to petroleum notably reduces its tendency 

 to ignite. No attempt, as far as we are aware, has yet 

 been made to utilize this singular property. 



EFFECTS OF TEMPEEATUKE ON THE ST. LOUIS BRIDGE. 



In the construction of the great steel bridge at St. Louis, 

 with its arches of 500 feet, calculations and allowances were 

 made for expansion and contraction by heat and cold 

 through a range of 140 Fahr., and the calculated difference 

 in the elevation of the centre arch of the upper chord above 

 the City Directrix on the hottest day of summer to the 

 coldest day of winter was about 18 inches. Ever since the 

 completion of the bridge, the height of the centre piers of the 

 top chords of the arches above the City Directrix has been 

 noted almost daily at temperatures which have ranged from 

 92 to 15 Fahr., and with the following results (the height 

 is that of the centre pier of the top chord above the City 

 Directrix) : 



Date. Temp., 3 P.M. Height in Feet. 



May 6, 1874 69 Fahr. 63.548 



June 29, 1 874 77 Fahr. 63. 688 



July 20, 1874 91 Fahr. 63. 7.57 



Jan. 4, 1875 10 Fahr. 63.241 



Jan. 9, 1875 15 Fahr. 63.065 



Between the temperatures of the 20th of July (the hottest 

 day of last summer) and the 9th of January (the coldest 

 day of last winter) there is a difference of 106 Fahr., and 

 a difference in height of 0.692 foot, or nearly 8-j^ inches. 

 The actual effect upon the structure, it will be observed 

 from this statement, is much less than the calculated eff*ect 

 (which, for a variation of 107, should have given a differ- 

 ence in height of nearly 14 inches). The difference is ex- 

 plained to be due partly to the protection afforded by the 

 roof of the bridge, and partly to the fact that the iron-work 

 is painted white, thus lessening the absorption of heat. Cor- 

 o'esp. Railioay World, Philadelphia. 



