Spontaneous combustion is at present very little understood, though chemists have of late turned their attention to the subject. It forms, however, no inconsiderable item in the list of causes of fires. There can be no question that many of those that occur at railway stations and buildings are due to the fermentation which arises among oiled rags. Over-heating of waste, which includes shoddy, sawdust, cotton, &c., is a fearful source of conflagrations. The cause of most fires which have arisen from spontaneous combustion is lost in the consequence. Cases now and then occur where the firemen have been able to detect it, as, for instance, at Hibernia Wharf in 1846, one of Alderman Humphery’s warehouses. It happened that a porter had swept the sawdust from the floor into a heap, upon which a broken flask of olive-oil that was placed above dripped its contents. To these elements of combustion the sun added its power, and sixteen hours afterwards the fire broke out. Happily, it was instantly extinguished; and the agents that produced it were caught, red-handed as it were, in the act. The chances are that such a particular combination of circumstances might not occur again in a thousand years. The sawdust will not be swept again into such a position under the oil, or the bottle will not break over the sawdust, or the sun will not shine in on them to complete the fatal sum. It is an important fact, however, to know that oiled sawdust, warmed by the sun, will fire in sixteen hours, as it accounts for a number of conflagrations in saw-mills, which never could be traced to any probable cause.

By means of direct experiment we are also learning something on the question of explosions. It used to be assumed that gunpowder was answerable for all such terrible effects in warehouses where no gas or steam was employed; and as policies are vitiated by the fact of its presence, unless declared, many squabbles have ensued between insurers and insured upon this head alone. At the late great fire at Gateshead, a report having spread that the awful explosion which did so much damage arose from the illicit stowage of seven tons of gunpowder in the Messrs. Sisson’s warehouse, the interested insurance companies offered a reward of 100l. to elicit information. The experiments instituted, however, by Mr. Pattinson, in the presence of Captain Du Cane, of the Royal Engineers, and the coroner’s jury impanelled to inquire into the matter, showed that the water from the fire-engine falling upon the mineral and chemical substances in store, was sufficient to account for the result. The following were the experiments tried at Mr. Pattinson’s works at Felling, about three miles from Gateshead:—

“Mr. Pattinson first caused a metal pot to be inserted in the ground until its top was level with the surface; and having put into it 9 lbs. of nitrate of soda and 6 lbs. of sulphur, he ignited the mass; and then, heating it to the highest possible degree of which it was susceptible, he poured into it about a quart of water. The effect was an immediate explosion (accompanied by a loud clap), which would have been exceedingly perilous to any person in its immediate vicinity. The experiment was next made under different conditions. The pot into which the sulphur and nitrate of soda were put was covered over the top with a large piece of thick metal of considerable weight; and above that again were placed several large pieces of clay and earth. It was deemed necessary to try this experiment in an open field, away from any dwelling-house, and which admitted of the spectators placing themselves at a safe distance from the spot. The materials were then ignited as before; and when in the incandescent state, water was poured upon the mass down a spout. The result was but a comparatively slight explosion, and which scarcely disturbed the iron and clods placed over the mouth of the vessel. Another experiment of the kind was made with the same result. At length, a trial having been made for the third time, but with this difference, that the vessel was covered over the top with another similar vessel, and that the water was poured upon the burning sulphur and nitrate of soda with greater rapidity than before, by slightly elevating the spout, the effect was to blow up the pot on the top into the air to a height of upwards of seventy feet, accompanied by a loud detonation. With this the coroner and jury became convinced that, whether or not the premises in Hillgate contained gunpowder, they contained elements as certainly explosive, and perhaps far more destructive.”

We may here mention, as a curious result of the Gateshead fire, that several tons of lead, whilst flowing in a molten state, came in contact with a quantity of volatilized sulphur. Thus the lead became re-converted into lead-ore, or a sulphuret of lead, which, as it required to be re-smelted, was thereby debased in value from some twenty-two to fifteen shillings a ton.

The great fire, again, which occurred in Liverpool in October last, was occasioned by the explosion of spirits of turpentine, which blew out, one after another, seven of the walls of the vaults underneath the warehouse, and in some cases destroyed the vaulting itself, and exposed to the flames the stores of cotton above. Surely some law is called for to prevent the juxtaposition of such inflammable materials. The turpentine is said to have been fired by a workman who snuffed the candle with his fingers, and accidentally threw the snuff down the bunghole of one of the barrels of turpentine. The warehouses burnt were built upon Mr. Fairbairn’s new fireproof plan, which the Liverpool people introduced some years ago, at a great expense to the town.

Water alone brought into sudden contact with red-hot iron is capable of giving rise to a gas of the most destructive nature—witness the extraordinary explosions that are continually taking place in steam-vessels, especially in America, which mostly arise from the lurching of the vessel when waiting for passengers, causing the water to withdraw from one side of the boiler, which rapidly becomes red hot. The next lurch in an opposite direction precipitates the water upon the highly-heated surface, and thus the explosive gas, in addition to the steam, is generated faster than the safety-valves can get rid of it.

A very interesting inquiry, and one of vital importance to the actuaries of fire-insurance companies, is the relative liability to fire of different classes of occupations and residences. We already know accurately the number of fires which occur yearly in every trade and kind of occupation. What we do not know, and what we want to know, is the proportion the tenements in which such trades and occupations are carried on, bear to the total number of houses in the metropolis. The last census gives us no information of this kind, and we trust the omission will be supplied the next time it is taken. According to Mr. Braidwood’s returns, for the last twenty-one years, the number of fires in each trade, and in private houses, has been as follows:—

Private Houses 4,638
Lodgings 1,304
Victuallers 715
Sale-shops and Offices 701
Carpenters and Workers in Wood 621
Drapers, of Woollen and Linen 372
Bakers 311
Stables 277
Cabinet-makers 233
Oil and Colour-men 230
Chandlers 178
Grocers 162
Tinmen, Braziers, and Smiths 158
Houses under Repair and Building 150
Beershops 142
Coffee-shops and Chophouses 139
Brokers and Dealers in Old Clothes 134
Hatmakers 127
Lucifer-match makers 120
Wine and Spirit Merchants 118
Tailors 113
Hotels and Club-houses 107
Tobacconists 105
Eating-houses 104
Booksellers and Binders 103
Ships 102
Printers and Engravers 102
Builders 91
Houses unoccupied 89
Tallow-chandlers 87
Marine Store Dealers 75
Saw-mills 67
Firework-makers 66
Warehouses 63
Chemists 62
Coachmakers 50
Warehouses (Manchester) 49
Public Buildings 46

If we look at the mere number of fires, irrespective of the size of the industrial group upon which they committed their ravages, houses would appear to be hazardous according to the order in which we have placed them. Now, this is manifestly absurd, inasmuch as private houses stand at the head of the list, and it is well known that they are the safest from fire of all kinds of tenements. Mr. Brown, of the Society of Actuaries, who has taken the trouble to compare the number of fires in each industrial group, with the number of houses devoted to it, as far as he could find any data in the Post-office Directory, gives the following average annual percentage of conflagrations, calculated on a period of fifteen years:—