April I, 1875] 



NATURE 



437 



application of preparations called boiler-compositions, of which 

 there are many varieties, their general action being to prevent 

 more or less effectually the carbonate and sulphate of calcium 

 and other impurities in water, which are separated by its ebulli- 

 tion and evaporation, from producing hard impenetrable crusts 

 or coatings upon the inner surfaces ot the boiler. The judicious 

 employment of a good anti-fouling preparation, and the thorough 

 periodical cleansing of tlie interior of boilers, go far to guard 

 against that source of danger ; though, in adopting measures to 

 diminish the formation of incrustations, care must also be taken 

 to avoid promoting internal corrosion of the boiler by the agents 

 used. 



The operations of the Manchester Steam Users Association 

 for the prevention of steam-boiler explosions, founded, mainly 

 through the instrumentality of Sir William Fairbairn, twenty 

 years ago, and of which Sir Joseph Whitworth has also been a 

 warm supporter from its commencement, appear to have gradu- 

 ally succeeded in very importantly reducing the annual number 

 of boiler explosions by introducing among its members a system 

 of periodical independent inspection. The Association will not 

 allow that the term "accidental," or mysterious, is applicable to 

 steam boiler explosions. Mysterious they certainly are not, as 

 they are generally quite traceable to causes which may be 

 obviated, such as inferior material or defective construction, or 

 local injuries, gradually developing and increasing, which would 

 certainly be discovered before they attained dangerous dimen- 

 sions, by a proper inspection. 



The following data with respect to the causes of boiler explo- 

 sions are taken frcm a table prepared by l\lr. L. Fletcher, chief 

 engineerof the Association :— 40per cent, were due ( from Jan. 1 861 

 to June 1870) to malconstruction of the boilers ; 29 per cent, to 

 " defective condition " of the boilers ; 15 per cent, to the failure 

 of seams of rivets at the bottom of externally fired boilers ; 10 

 per cent, to overheating from shortness of water ; and less than 

 3 per cent, to accumulation of incrustations. 



An examination into the particular nature of the services per- 

 formed by boilers which have exploded shows that a considerable 

 number of explosions have occurred at ironworks, and a very 

 large proportion at collieries, where plain cylindrical externally- 

 fired boilers are much used. Many of the explosions of these 

 particular boilers arise from places which remain for a time con- 

 cealed in the overlaps of the seams of rivets, defying detection, 

 but gradually extending from one rivet hole to another, till some 

 -udden strain causes them to extend throughout the entire seam, 

 the boiler splitting in two. The particular description of boiler 

 which gave rise to the largest number of fatal accidents during 

 the year taken as illustration was the single-flued or Cotnish 

 boiler ; and it was stated by Mr. Fletcher that all these explo- 

 sions must have been the result of glaring neglect, as there is no 

 boiler safer to use wlien well made and properly cared for. The 

 simple precaution of strengthening or giving internal support to 

 the sides of the furnace-tube of these boilers, the importance of 

 which was demonstrated many years ago by .Sir W. Fairbairn, 

 appears to be still greatly neglected, the result being the frequent 

 collapse of the tube through weakness. Very few explosions in 

 1873 appear to have been due to the neglect of the attendants, 

 but by far the greater number to that of the boiler owners or the 

 makers. 



[The lecturer then gave a number of instances strikingly illus- 

 trative of the statements above made.] 



Tlie foregoing and other very numerous illustrations of the 

 appalling display of ignorance, neglect, or recklessness in deal- 

 ing with the application of steam power, point strongly to the 

 importance of legislation connected with this subject. There 

 can be no reason why il i itsponsibility of the proper condition 

 of boilers and steam z\ 1 i atus generally should not be thrown 

 upon inspectors, just as ilie proper fencing of machineiy in fac- 

 tories, and the proper condition of steam boilers in a passenger 

 steamship, are secured by a system of responsible official in- 

 spection. 



The explosions which are often recorded as occurring in kitchen 

 ranges and in boilers used in connection with the heating of 

 buildings are not unfrequently attended by fatal results. Rluch 

 of what has been said with regard to boiler explosions generally 

 applies to accidents of this class. 



As the water in kitchen boilers is often used for culinary 

 and drinking purposes, the means employed in boilers used for 

 steam purposes only, to prevent the foimation of hard deposits, 

 cannot be resorted to ; therefore the only means of guarding 

 against accidents to domestic boilers from these causes consists 



in frequent and thorough cleaning out, which is especially neces- 

 sary where the water supply is hard. 



Explosions also occur with household boilers of the ordinary 

 circulating class, unprovided with safety valves, through the stop- 

 taps of the pipes which connect them with an overhead cistern 

 being left closed by accident or negligence, in which case steam 

 pressure must speedily accumulate to a d.ingerous extent, all 

 outlets being closed. Accidents with such boilers are particu- 

 larly liable to occur during severe frosts in consequence of the 

 circulating pipes becoming plugged up with ice, whereby the 

 outlet for steam pressure is as completely cut off as if the stop- 

 taps were closed. .Several accidents due to these two causes, 

 some of them attended by fatal results, were recorded last year. 

 The obvious and simple method of guarding effectually against 

 such explosions is to have the boiler fitted with a reliable 

 safety valve, of the most simple form. 



Explosions resulting from tlie ignition of mixtures of in- 

 flammable gas and air constitute even a more formidable class 

 than that just described, for the number of explcsions in ccal 

 mines which occur in a year is very considerably greater than 

 that of boiler explosions, while the loss of life occasicned by 

 the former is very considerable, and is occasionally appalling 

 in its magnitude. 



If marsh-gas, or light carburetted hjdrogen, which exists 

 imprisoned in coal-beds and escapes into the atmosphere in the 

 pit-working, either gradually or sometimes under considerable 

 pressure, becomes mixed with the air to such an extent that 

 there are about eighteen volumes of the latter to one of the 

 gas, the mixture burns witli a pale blue flame, which will 

 surround that of a candle contained in such an atmosphere ; 

 the appearance of such a "corpse light" round the flame of 

 the pitman's cardie or lamp-flame is a warning, too generally 

 unheeded, of the presence of fire-damp in quantities likely 10 

 be dangerous, for if the proportion of marsh-gas increases much 

 lieyond that above specified, an explosive atmosphere will le 

 formed, the \iolcnt character of which increases as the propor- 

 tion of fire-damp appri aches that of one volume to ten of air. 

 Marsh-gas requires for its ignition to be brought into contact 

 with a body raised to a white heat ; fire-damp, cr a niixtuie 

 of marsh-gas and air is therefore not inflamed by a spark or 

 red-hot wire, but will explode if brought into contact with 

 flame. The fact that this contact must be of some little 

 duration to ensu'e the ignition of the fire-damp was appl'ed by 

 Stephenson in the construction of his safety-lamp; and a very 

 philosophical application of the property possessed hyigcod 

 conducting bodies, such as copper or iron, of cooling down 

 a flame below the igniting point of the gas, and thus exin- 

 guishing it, was made by Davy in the conslruct'on of his 

 safety-lamp. 



All the efforts of eminent scientific and practical men, for 

 the better part of a century past, to diminish the number of 

 coal-mine explosions by improving the ventilation of the mines 

 and providing the miner with comparatively safe means of illu- 

 mination, appear to have had very little effect in reducing the 

 number and disastrous nature of these accidents. Since the 

 construction of safety miners' lamps by Davy, Stephenson, and 

 Clenney, repeated and partially successful efforts have been 

 made to reduce the loss of light consequent upon the necessary 

 enclosure of the flame, and thus to lessen the temptation of 

 the miner to employ a naked flame at his work in fiery mines ; 

 yet investigations after mine explosions still frequently disclose 

 instances of the employment of candles where they are un- 

 doubtedly dangerous, and the regulations which have been 

 made law with the view of preventing accidents through the 

 use of naked lights by miners, where theie appears any likeli- 

 hood of fire-damp esoping and lodging, are in many cases 

 either habitually neglected or very carelessly carried out. One 

 practice which appears to have become very general in mines 

 where fire-damp is known to exist, that of sending firemen 

 with safety-lamps to examine the mines, the men then pro- 

 ceeding to work with naked lights in all places marked as safe 

 by those officials, is obviously a most dangerous one, the lives of 

 many being made absolutely dependent upon the vigilance and 

 trustworthiness of one or two ; yet it appears to be one almost 

 forced upon the managers of collieries by the men themselves, 

 wlio often absolutely refuse to go to work with safety-lamps. 

 Of the three collieiy accidents which occurred between Dec. 23 

 •and Jan. 7 last, by which twenty-eight men lost their lives, two 

 afford sad illustrations of the fact that the overlookers and the 

 miners themselves are chiefly to blame for the frequency of these 



