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May I, I8CS.J THE CIVIL ENGINEER AND ARCHITECT’S JOURNAL. 133 ance ; and it is exactly in their ease that the regulations of the Board of Trade are said to be often disregarded. Amongst the means of saving or protecting life, should he mentioned two electric mining lamps, one set in action by a coil, the other by a peculiar form of battery ; it is also proposed to try a manganese battery, which may be almost dry. It is stated also that another lamp, which will burn under water, or elsewhere, without any connexion with the outer air, or any battery, for a considerable time, has been invented by two pupils of the Polytechnic School of Paris, but the construction is not yet made known in England. Great doubts have been thrown over the feasibility of electric lamps for mining pur poses, but in Prance considerable trouble is being taken to carry the idea into practice. The collection of models and plans of vessels is highly in teresting. The class includes more than eighty exhibitors from all countries—France, Holland. Belgium, Denmark, Swe den. and Norway, and the United States. The British exhibitors, including the Channel Islands and the colonies, number more than twenty, or a quarter of the whole. The class of sea and river fishing apparatus and tackle pre sents a good deal of interest, particularly « ith respect to the various kinds of nets and traps used in France, of which there is a great variety. England contributes half-a-dozen exhibit- tors ; but there are not more than two or three from all the other exhibiting countries. Holland, however, shows some remarkable models of fishing-boats in another class; one in particular, which obtained a gold medal at the Hague Exhibi tion last year, and is sent by the Dutch Government as a pre sent to the town of Havre. In other classes will be found a considerable number of anchors, windlasses, capstans, forms of sails, systems of rig ging, methods of reefing, &c., presenting many novelties. On the whole, the first group of the exhibition, that which forms the distinguishing characteristic of a maritime exhibi tion. must be regarded as satisfactory. Some of the classes might have been more fully represented, but the collection is large, and, fortunately, there are few objects which do not pre sent points of attraction. STEAM BOILER EXPLOSIONS. The following is abstracted from the recent Report of the Chief Engineer to the “ Association for the Prevention of Steam Boiler Explosions,” and contains statements of facts which can not be too generally known. The Report states that No. 16 explosion, by which one man was killed, occurred to a boiler on board a small screw steamer, employed for towing purposes in a floating basin. The steamer was a wooden one, 50 feet in length. 10 feet in width, and propelled by a screw 2 feet 6 inches in diameter, driven by a single direct acting inverted high-pressure engine, which exhausted into the funnel of the boiler. The steamer was engaged to move a vessel of 800 tons burthen, and the steam, as is usual in such cases, was well up in order to make a fair start. It appears that soon after setting to work the tow rope parted, and that the engine stood while a new rope was attached, when, just after the engine had been set to work again, and had run for a minute or two, the explosion occurred. The boiler was cylindrical and of multitubular construction, having a single flue tube running into a combustion chamber at the back, from which a number of small flue tubes returned to the smoke box at the firing end. The shell was 7 feet 9 inches in length by 5 feet 4 inches in diameter, while the thickness of the plates was three-eighths of an inch in the cylindrical portion, and seven-sixteenths of an inch in the flat ends, the furnace tube being 6 feet long by 2 feet 7| inches in diameter, and made of four plates laid longitudinally, which had been originally a quarter of an inch in thickness. There were two safety-valves, one of dead-weight construction, and the other loaded with a spring balance, both of which were defective as hereafter explained, while in addition there was no steam pressure gauge. The boiler gave way in the furnace tube, which collapsed at the crown, rending transversely about midway in its length, and also from one end of the tube to the other at one of the longitudinal seams of rivets. The rush of steam and hot water that took place consequent on these rents, carried away the furnace mountings and fire bars, knocked down the engine, tore up the after part of the deck, and swept away a portion of the boat’s stern, while the engineer, who was standing on the step-ladder, was blown up into the air, and falling into the water, died a few hours after his extrication by drags. A dded to this, the vessel in tow- was set on fire by a quantity of live coals thrown into the foresail, but fortunately the tug-boat was not sunk, and the man at the wheel escaped unhurt. The cause of the collapse is complex. The furnace tube was not strengthened as it should have been with encircling hoops or other suitable provision, while the plates, which had been only a quarter of an inch thick originally, had suffered from wear and tear, being cracked at several of the rivet holes over the fire, and reduced at the crown by internal corrosion to the thickness of three-sixteenths of an inch from one end of the tube to the other, so that it was seriously weakened and unfit to stand the pressure of 621b. on the square inch, to which the dead weight valve was loaded. In addition to the weakness of the furnace tube, both the safety-valves were so defective that there was great liability to excessive pressure. The dead weight valve was most contracted in area, being barely one inch and five-sixteenths in diameter, while the lift was only three-sixteenths of an inch, and the steam way so choked by the central spindle which carried the dead-weight that the effective area for allowing the escape of the steam was little more than half of a square inch. The other valve, which was loaded by a spring balance, was altogethcx - false in its indica tions, the proportions of the level’ to the diameter of the valve being such, that for every pound indicated on the index there w as upwards of one and a half pounds on the valve, and with the pointer at 601b., which was the ultimate range of the index, the actual pressure was 981b. Added to this, there was no stop ferrule to prevent the spring’s being overscrewed, and thus the valve jammed fast. It is reported that the engine man was seen to screw down the valve but a few minutes before the explosion took place, but as the parts were altogether dismantled by the explosion, it was impossible at the time of examination to determine to what point the valve may have been loaded. Thus it appears that the furnace tube was weak from its dilapidated condition, and both safety-valves defective, so that the boiler laboured under a complication of disorders. It may be difficult correctly to adjudicate to each one of these its precise share in the cause of the explosion, but it is clear that the catastrophe arose from the generally defective state of the boiler, and that it would not have occurred had the safety- valves been efficient and the furnace tube well constructed and maintained in good condition. At the inquest, though the coroner instructed the jury that it was their duty to consider whether there had been anything radically wrong either with regard to the boiler or its condi tion, yet he recommended the jury, notwithstanding the facts just alluded to, to return a verdict of “Accidental death.” with which they complied. No attention appears to have been drawn to the condition of the boiler or the unsatisfactory state of the safety-valves. Such verdicts afford complete immunity to steam users to work on defectively equipped and worn out boilers, and it may here appropriately be stated that in the port in question five explosions have occurred on board tug boats of a very similar class to the one under consideration. In one of these explosions, which took place eighteen years since, as many as fifteen persons were killed, while in another, which happened nearly two years ago, two boilers exploded simultaneously, killing five persons. As I am in possession of the particulars of this latter explosion, which are of interest, and were not given at the time in the Association’s Monthly Reports, they may briefly be referred to on the present occa sion. The explosion was included in the table of 1866 ks No. 50. The particulars are briefly as follows :— No. 50 explosion, 1866, by which five lives were lost, occurred at half-past one o’clock on the afternoon of Thursday,November 1st, on board a steam-tug, when its two boilers exploded simultaneously, just as she was towing a vessel out of port. The tug-boat was a wooden one propelled by paddles, while both its boilers were of peculiar construction. They were neither truly cylindrical nor truly oval, and measured 8 feet 4 inches horizontally by 7 feet 5 inches vertically at the front, and tapered down at the back to 7 feet 3 inches by 7 feet, 29