654 THE POPULAR SCIENCE MONTHLY. 



"Tobacco-smoking," "Spontaneous ignition," and lastly "Incendiar- 



ism." 



There is no doubt that many a fire owes its origin to causes quite 

 beyond the control of the tenant of the house in which it occurs, and 

 that the scamping manner in which builders' work is often done is the 

 prime cause of many a fire which is put down as unaccounted for. The 

 ends of joists are left protruding into chimnej^s, or a thin hearthstone 

 is set upon a bed of timber. In both cases the wood becomes so dry 

 and hot that it is ready to take fire from the first spark that settles near 

 it. Overheated flues represent a source of danger which is also attrib- 

 utable to the careless builder ; for, if the flue were so placed that its hear 

 could not affect adjacent woodwork, it would be always as safe when 

 hot as when cold. It is true that by act of Parliament builders are 

 obliged to preserve a certain distance between flues and timber ; but 

 surveyors can not always reckon on their instructions being carried 

 out, and cases are unfortunately rare nowadays where workmen will do 

 their duty in such matters without constant supervision. Lath-and- 

 plaster divisions between houses are also illegal ; but buildings, and 

 more especially warehouses, are now of such vast extent that they really 

 represent aggregations of small houses in which the act of Parliament 

 concerning party-walls becomes a dead-letter. 



Among the ascertained causes of fire are those which occur in the va- 

 rious workshops where hazardous trades are carried on. These naturally 

 show an increase since steam-power has become such a universal aid to 

 nearly every kind of human labor ; necessitating furnaces which remain 

 kindled for weeks or months together. Apart from this source of risk, 

 there are numerous trades where such inflammables as turpentine, naph- 

 tha, spirits of wine, and combinations of them in the form of varnisheiS, 

 are in daily use to a very large extent. The familiarity which such con- 

 stant use provokes breeds a contempt which often resolves itself into a 

 negligence almost criminal in its nature. Drying-stoves afford another 

 dangerous item in the list of fires connected with the trades ; japanners, 

 cabinet-makers, and hosts of others using such stoves as a necessity of 

 their business. Hot -water pipes for heating purposes also represent the 

 cause of a large number of fires, the most dangerous kind being those 

 which are charged with water and hermetically sealed. The reason of 

 this is easily explained. Water boils at a temperature far below that 

 necessary to ignite woodwork ; but, when confined in such pipes as we 

 have described, it will rise in temperature to an extent only measured 

 by the strength of the material which holds it. A soft metal plug is 

 sometimes inserted in these pipes, so that, should any unusual degree 

 of heat be approached, it will melt out, and thus relieve the pressure ; 

 but such a good precaution is by no means universal. 



The pipes which are used for carrying off heated air, and which are 

 placed above gas-burners, are too often allowed to pass between the ceil- 

 ing and the floor above without any regard to the obvious danger in- 



