Makch 10, 1899.] 



SCIENCE. 



363 



hind two supporting walls or piers, the ash 

 from the wood fires which were burned in 

 the rooms above. These hickory ash pits, 

 as they were styled, were south of and 

 directly in line with the passage leading to- 

 ward the iron screen. Tliis series of com- 

 partments was on the extreme west of the 

 sub-basement. A few of the exterior com- 

 partments of the sub-basement received a 

 very little daylight, but all the rest was 

 wholly dependent on artificial light and 

 sevei'al gas jets were kept constantly hghted. 

 In the center of the sub-basement, under 

 the dome, was a large gas meter connected 

 to a 4-inch main and having on its outlet 

 en'd a 200-light glycerine gas governor. 

 This meter had not been in use for some 

 time, and the inlet valve was closed, 

 but the outlet valve was open, and it 

 was discovei'ed afterwards that this outlet 

 pipe was also connected with a live 4-inch 

 main. The explosion occurred about 5:15 

 p. m. , and its effects were observed over 

 47,000 cubic feet of the basement and up- 

 ward quite to the dome. By the explosion 

 the brick arches, covered with earth and 

 then with heavy stone pavement slabs, were 

 torn iTp, brick partitions and supporting- 

 walls were overthrown, stout locked doors 

 on the upper floors were torn open, and 

 there was a general wrecking of all the 

 lighter structural parts. Observation of 

 the lay of the wreckage showed conclu- 

 sively that it radiated in all directions from 

 a point about the gas meter, and that the 

 most violent effects were in general at the 

 points most distant from this center. The 

 most \'iolent effect of all was on the west, 

 where the heavy gTanite screen wall form- 

 ing the fagade of the building was displaced 

 by IJ inches, and the stout wire protecting 

 screen about the engine was forced into a 

 depth of two feet from the original plane 

 for an area of three feet in diameter, and 

 many of the stout rods were ruptured. 

 Searching examination showed that no ex- 



plosive or other explosive-forming material 

 than illuminating gas could have been pres- 

 ent ; that for tliirty minutes prior to the ex- 

 plosion there was for some reason a gas pres- 

 sure of twice the normal ; that under an ex- 

 cessive pressure gas would flow thi'ough the 

 governor, and that this could furnish suffi- 

 cient gas to do the work accomplished 



The gas had a specific gravity of 0.601, 

 and as it escaped it flowed through the 

 devious passages and compartments, filling 

 first the pockets with mixtures of various 

 proportions and settling lower and lower 

 until the stratum reached down to the level 

 of the burning gas jets where it was fired. 

 These were near the meter, where, of course, 

 the gas would be richest. Here was the 

 region of combustion. As the tongue of 

 flame rushed under the low archways and 

 through the passageways to the higher 

 vaults beyond, it produced a violent disturb- 

 ance of the atmosphere, thoroughly com- 

 mingling the gas and air and throwing a 

 mass of inflamed gas into their midst, thus 

 producing a greatly accelerated combustion 

 and explosion. When this tongue of flame 

 burst into the compartment containing the 

 hickory ash this dust was also intimately 

 commingled with the gas-laden atmosphere, 

 and here was produced the most violent of all 

 the effects manifested ; for the granite 

 screen wall that was displaced was on the 

 right side of the hickory ash pits, and the 

 stout wire screen that was perforated was 

 directly in front of them and at the end of 

 the low and narrow passage leading from 

 the vault containing these pits ; and fur- 

 ther the most violent effects produced on 

 the upper floors, quite to the top of the 

 building, were about the spiral staircase 

 leading from the compartment containing 

 the wire screen and which was but a con- 

 tinuation, thi-ough the low, narrow passages 

 of the compartment containing the hickory 

 'ish. Charles E. Munroe. 



Columbian Ukiveesity. 



