LECTURES. ]79 



and reported on than was customary at present. He had found in 

 some cases, even recently, that the fresh air intended for the supply 

 of a pit, where there were hundreds of men at work, was contaminated 

 largely when the wind blew in a particular direction from a large 

 heap of waste fuel of inferior quality that had been burning there for 

 many previous years. He mentioned this merely as one of the numer- 

 ous instances which could be pointed out of the impossibility of check- 

 ing evils of great magnitude, where more intelligence did not prevail 

 in respect to the nature of the materials which were employed. 



One of the shafts of access to the pit, or mine, was usually converted 

 into a ventilating flue, by kindling a large fire, not at the bottom of 

 the pit, but at one side, near the bottom. From this a large flue con- 

 vej'ed the vitiated air and products of combustion to the shaft, at a 

 sufficient distance above the lower part to permit them to cool on the way 

 to a degree which would allow men and materials to pass safely up 

 and down the shaft. Dangerous atmospheres were sometimes diluted 

 with air, by proportionate ventilation, so as to take away all risk of 

 explosion; or discharged by a separate shaft, or by a separate channel, 

 into the ordinary ventilating shaft, far above the fire, so as to pre- 

 vent their coming in contact with flame. Mechanical appliances were 

 used in some mines to promote ventilation, and advantage had also 

 been taken in different places of the steam jet. Choke damp (car- 

 bonic acid) infested numerous mines, and was frequently a cause of 

 death. The Davy lamp, though an invaluable invention, was not 

 always to be trusted, even with all the improvements that had been 

 suggested in recent times. An infinitesimally small particle of carbon 

 might be projected, sufficiently hot from the flame of the lamp, 

 through the wire gauze, by a sudden commotion of the air arising from 

 the falling in of any portion of the roof of amine, or any other cause, 

 and be fanned into an active combustion in an explosive atmosphere, 

 though ordinary flame is entirely arrested by the wire gauze pro- 

 posed by Davy. 



Again, in many mines, partitions of wood giving way^ from the 

 decay of the material, rendered the ventilation less effective ; and, in 

 short, from the length of the air courses, extending sometimes to ten, 

 twenty, or thirty miles, the underground miner almost always worked 

 in an atmosphere more or less contaminated ; and he did not consider 

 that sufficient exertions were made at present, either by the extended 

 application of practical science, or by the education of the miner, to 

 place this subject on the footing demanded both by the dictates of 

 humanity and by a true economy as a matter of business. 



The ventilation of ships had made less satisfactory progress, prob- 

 ably, than that of any other cases in which ventilation was so im[)or- 

 tant. From the time of Dr. Hales, who had long since entered on 

 this question practically, with great ability, and at a period when 

 much of the information now made accessible by more modern chem- 

 istry was not available, it had at different periods been taken up, and 

 again neglected ; and even in his own experience he had seen it alter- 

 nately prosecuted with vigor, and abandoned by successive directors of 

 the same board, according as their appreciation or want of information 

 as to the laws of health had dictated. The sea had had its ''black 



