720 Transactions of tee American Institute. 



inches deep, and perforated at the center line by the holes for the 

 rivets. The side-plates were braced together every eight and three- 

 quarter inches one way and nine and one-fifth inches the other way 

 of their surface, by bolts of one and one-eighth inch diameter with 

 threads cut upon each end and screwed into corresponding thread* 

 cut in the plates over which both ends of the bolts were slightly — and 

 but very slightly — riveted. The box was placed on one edge upon 

 an eight inches thick brick-wall, and was inclosed with side-walls of 

 brick and masonry, with the exception of a strip fifteen inches deep 

 at the top and twelve inches wide at one side, which protruded into 

 the air, and to which the gauges were attached. The inclosed por- 

 tion of the box was heated by two small furnaces without intercom- 

 munication, the fire-grates of each being twenty-seven inches long and 

 fourteen inches wide. The fuel was wood, and the products of combus- 

 tion were discharged through two sheet-iron pipes. The surface of 

 the box exposed to the fire was nineteen and a half square feet, and 

 was all water-heating surface, as the box was filled with water to 

 within nine inches of its top. Of the total interior height of the 

 boiler, therefore, thirty-seven inches were occupied by water and 

 seven inches by steam. 



The fires being brought to steady action, and steam raised to the 

 atmospheric pressure, the opening for the escape of the latter was 

 closed, and the pressure rose as follows, for the corresponding times, 

 namely : 



Steam-pressure in 

 Time p. m. pounds per square 



, > v inch above the 



Hours. Minutes. atmosphere. 



3 18 



3 20 4 _ 



3 21 5 



3 22 7 



3 23 9 



3 24 11 



3 25 13 



3 26 15 



3 27 18 



3 28 20 



3 29 23 



3 30 27 



3 31 30 



3 32 34 



3 33 38 



3 34 44 



3 35 49 



3 36 51 



3 37 54 



