178 LECTURES. 



gunpowder, wliicli was not at first in any way affected Ly it. 

 The flame was blown out, and rekindled. This was repeated sev- 

 eral times in succession. At last the gunpowder was exposed, the 

 level of the burning fluid having descended below the surface of the 

 central portion. Still it did not fire ; it was surrounded and enve- 

 loped in a vapor of oil rising rapidly from the portion below. At last, 

 the oil being nearly consumed, and the edge of the flame coming in 

 contact with individual grains, they deflurated one by one, and soon 

 afterwards the rest of the gunpowder exploded. 



This experiment was then varied by placing a small portion of 

 gunpowder on a flat brick, drenching it with oil of turpentine, and 

 sustaining continually around it a small portion of this fluid. A 

 light was then applied, when the oil alone was kindled ; the gun- 

 powder acting as a wick, and remaining totally unaffected so long as 

 there was any oil in the vicinity to be consumed. 



It was then argued that general instruction in chemistry would 

 give a similar power of control over many sources of fire, and that 

 tli^e principles he had explained in connexion with this illustration 

 could in many cases be practically applied. It would also lead to 

 the more extended use of fire-proof or incombustible materials in 

 all classes of building, by giving correct views as to their nature and 

 capabilities, and the advantages attending their introduction. 



The next subjects were the ventilation of underground mines and 

 of ships. These presented peculiar and somewhat similar difficulties, 

 from the comparative inaccessibility of the lower portions of both to 

 the direct access of atmospheric air. 



In the class of mines to which he adverted_, the great difficulty lies 

 principally in the expense of making ventilating shafts, particularly 

 where springs of water interrupt their formation, or the presence of 

 fire-damp render it important to have a larger amount of ventilation 

 than would otherwise be requisite. Nothing would contribute so 

 much to the better ventilation of mines as the invention of machinery 

 and apparatus for facilitating the sinking of shafts. The attention 

 of men of science and practical engineers should bo directed specially 

 to this subject. Hitherto he had not had the opportunity of visiting 

 mines in this country, but he had examined many mines in Great 

 Britain, more especially in the northern mining district, on which he 

 had reported officially when acting on a commission of health for 

 cities and populous districts in England and Wales. In some of the 

 most dangerous mines in England a very slight interruption to the 

 ventilation, or a fall of tlie barometer, causing a rapid discharge of 

 fire-damp from the coal, greatly increased the risk of explosion. 

 Hundreds were at times subjected to the most horrible deaths, the mix- 

 ture of fire-damp and air in numerous mines constituting, at the mo- 

 ment of explosion, a kind of aerial gunpowder that equally surrounded 

 the body and penetrated to the interior of the chest. In no range of 

 cases where ventilation was an absolute necessity would education in 

 science do more good than in the mining districts. It was not enough 

 to have a few able superintendents here and there. Every mine and 

 every district of a mine ought to be much more frequently examined 



