1882.] on Some of the Dangerous Properties of Busts. 91 



report, the accidents at flour mills appear, however, to have been 

 scarcely less nnmerous or disastrous than before the date of the 

 Tradeston catastrophe. Thus, in September 1874, a similar though 

 less serious explosion occurred at the Port Dundas City Mills, and in 

 May 1878, another flour-mill explosion, quite unparalleled for its 

 destructive effects, occurred at Minneapolis, Minnesota, where 

 eighteen lives were lost and six distinct corn mills were destroyed. 

 Mr. Peckham, writing after the event from the University at Min- 

 neapolis, states that two dull explosions rapidly succeeding each other 

 were heard by him, and on looking towards the manufacturing part of 

 the city a large volume of black smoke was seen to envelop the 

 spot where the Washburn A Mill stood, a column of smoke being at 

 the same time projected to a height of several hundred feet. A storm 

 was blowing at the time in the direction from the "Washburn ISIill to 

 other mills in the neighbourhood, and in about five minutes from the 

 time that the explosion was heard five neighbouring mills, with 

 adjoining premises, were in flames. Persons who were in close 

 vicinity to the scene of the calamity at the time of the first explosion 

 heard a succession of sharp hissing sounds, doubtless caused by the 

 very rapid spread of flame through the dust-laden air in the passages 

 leading from the mills to the exhaust box, and, at the instant of the 

 explosion, the Washburn A Mill was observed to be brilliantly illu- 

 minated from top to bottom. The nearest mill to the latter was 

 25 feet distant, and appears to have exploded directly the flames 

 burst through the first mill. The explosion of a third, 25 feet 

 distant from the second, followed almost immediately ; and the 

 other three mills, about 150 feet distant in another direction, 

 were at once fired. Windows were thrown out of buildings about a 

 quarter of a mile distant, consequent upon the back rush of air 

 following the explosion, and portions of the building materials were 

 projected to very considerable distances. The cause of the explosion 

 was carefully inquired into (by Messrs. Pick, Peckham, &c.), and it 

 was attributed to fire being generated by the stoppage of the feed to 

 a pair of stones, or by the accidental passage of some very hard 

 substance between them. The consequent explosion of dust-and- 

 air mixture round the stones and in the communicating passages 

 added, by its concussion, to the quantity of dust suspended in the air 

 in difterent parts of the mill, and a second more violent explosion 

 was thus immediately brought about. The attention of Professor 

 Lawrence Smith was directed to the subject of flour-mill explosions by 

 this accident, and, in a letter to M. Dumas, of May 4th, 1878, which 

 was published in the ' Annales de Chimie et Physique,' he states his 

 conviction, based upon experimental inquiry, that such accidents are 

 due to the formation of explosive mixtures of finely divided organic 

 matters (such as flour) with the air, and refers to this as a " revelation " 

 of the existence of a previously unknown danger connected with an 

 important industry, being apparently unaware of its elucidation by 

 Rankin and Macadam, and Watson Smith in 1872. 



