MECHANICS AND USEFUL ARTS. 105 



MEANS OF ARRESTING FIRES. 



Mi\ D. J. Murphy of Cork, Ireland, publishes the following plan for 

 arresting and extinguishing fires. 



"It is simply saturating the water discharged from fire engines with a 

 certain proportion of chloride of sodium (common salt) and potash, both cheap 

 articles; and, indeed, the former alone will be found quite effectual in all 

 ordinary cases. The proportion of these ingredients to be employed may vary 

 from one-tenth to one-thirtieth of the weight of the water so discharged, of 

 which it will be found that a considerably less quantity will be required, 

 from being so saturated. In low elevations, and where the flame has not 

 reached a great height, the stronger impregnation may be used with advan- 

 tage ; but when the flame has arrived at a considerable elevation, the weaker 

 impregnation can only be employed, arising from the greater resistance of the 

 air, the increased weight of the materials, and the augmented difficulty of the 

 stronger impregnation passing through the valves of the fire engine : though, 

 even then, it can be successfully discharged to attack the flame at its root or 

 base, which is, perhaps, the best course to adopt in all cases. A fireman, hi 

 his ordinary dress, and simply armed with an elastic tube conveying this 

 stronger impregnation, may boldly and securely face the strongest and fiercest 

 flame, and make himself a passage through it, by commencing cautiously 

 at first to discharge the impregnation on each side of him; for, where it 

 falls, it not only subdues the flame, but, by leaving a coating of the 

 materials, it prevents it from readily catching again the substance on which 

 it previously fed ; the result being that the muriatic acid becomes volatilized, 

 and flies off, while the soda, which is indestructible, is converted into a glaze 

 on the surface. The root or base of the flame is therefore the point to which 

 the force, power, and efficacy of the impregnation ought always to be directed. 



" This impregnation, it is to be observed, can be so managed, by the addi- 

 tion of other ingredients, when found necessary, or where the expense is 

 disregarded, such as the diluted mineral acids and their salts, as to produce a 

 temperature approaching, and even considerably below, the freezing point on 

 Fahrenheit's scale, and yet preserve its fluidity ; for it is by its chemical com- 

 bination it acts against the flame, and also in serving to reduce the temperature 

 of the surrounding heated atmosphere. The effect of several engines acting 

 at the same time, by the weaker and stronger impregnations, must be all 

 powerful, as may be easily conceived ; and no fire, whatever degree of head it 

 may have previously attained, can resist the power and efficacy of this impreg- 

 nation for any period exceeding half an hour. Even water, saturated with 

 finely powdered clay, chalk, slaked lime, &c., all cheap articles, and slow 

 conductors of heat, may be employed with great advantage on flames of low 

 elevation ; for it is to be impressed that water is alone used as a medium for 

 conveying these substances, as well as the others, to the body of the flame, or 

 rather to its source such as the substance on which it feeds. Let this be 

 completely coated with these ingredients; for the water will be quickly 

 evaporated by the intense heat, and the effect sought namely, the extinction 

 of the fire will be the immediate and necessary consequence." 



