The many obstacles in the way of making illuminating gas in portable apparatus have been very serious drawbacks in the successful operation of most of those heretofore offered to the public, the reasons being that the question is partly one of a chemical nature, and inventors, for the most part, mechanical people. Chemists rarely apply discoveries in a practical form, and mechanics are not sufficiently versed in the science to give it mechanical shape. This question re- quires a combination of the two sciences. Numbers of machines of all kinds have been made for making gas by passing atmospheric air through one of the volatile hydrocarbons; but owing to the fact that air does not combine with the vapor, together with other causes of failure, most of them have proved worthless, the vapor condensing in the pipes of the building, and chofeinjp the same when they reach the temperature of 40 Pan". " We are now called upon to notice an invention which the inventor claims has none of the objections which may be brought against many which have preceded it. The engraving is a vertical section of an apparatus invented by Mr. C. P. Dunderdale, of 90 Wall street, New York city, for generating hydrogen gas by immersing scraps of iron shavings into diluted oil of vitriol with water, as shown at D in the engraving. The hydrogen rises therefrom, as shown by the arrows, and enters the pipe, L, in a heated state, passes down the same, and rises through a hydrocarbon contained in a compartment as seen at C. Here combining with the vapors it passes out through valves at K into the holder, which, having its edges sealed with water, B, rises, and if the gas is not being used it lifts a basket out of the dilute acid containing the metal scraps, which then remains inactive until the gas is used, when it again begins to generate as fast as used. The gas formed is carbureted hydrogen, a rich and powerful illuminating agent. It cannot be set on fire in its pure state, and the apparatus is therefore non-explosive. It is burnt in the smallest sized common gas jets like coal gas, and the inventor assures us costs less than half the price of coal gas as charged by the New York gas companies. He further asserts that it only requires from one third to one fifth the quantity that is required of coal gas to give the same amount of light. The machine being automatic requires very little attention. F, G, H, I, J, and M are caps and pipes for feeding the machine and drawing off the gas and contents of the machine when necessary. The sat (sulphate of iron) precipitated in the bottom of the machine is valuable, being largely used in dyeing, tanning, ink making, etc., and if saved and sold will, it is claimed, sell for as much as the whole cost of the gas. The apparatus is made of material that is not affected or injured by the presence of the acid, and will last for years, and admit of a comparative low cost. This will interest all gas consumers. Full particulars and information relating to it can be had by addressing the inventor and manufacturer as above. IN our last number we alluded to the serious want of water in Philadelphia. There is water enough it seems in the river, but it has heretofore been made to pump itself up by turning turbine wheels, and the process wastes ten or twelve gallons for every one made practically available. Plans are maturing tor the construction of peimanent steam pumps, so as to prevent a recurrence of the alarming dearth of water under which the greater part of the city is now laboring. All the steam fire-engines of the city hare been called into requisition to pump water into the Fairmount reservoir. Two of them are on duty at a time, and their united efforts throw over 1,000,000 gallons into the reservoir in twenty-four hours. Method of Detecting .Poisonous Gases—The fias-ophaner. The Pioneer, England, states that a discovery has been made by an officer, which, if the results on a large scale are at all commensurate with the experiments made on a small one, may prove of great value in giving a timely indication of the approach or presence of that poisonous state of the atmosphere which is generally believed to precede cholera and other epidemic diseases. The gasophaners, or poisonous gas indicators, as the discoverer calls them, are easily and cheaply made. A piece of fused boracic acid, the size of a walnut, from which the water of crystallization has been expelled, is heated to redness in chlorine, or has dissolved in it while hot a small quantity of common salt, care being taken that there is not sufficient soda—16 per cent—to convert the boracic acid into borax, which would spoil the effect. The red-hot lump of boracic acid thus charged is blown with a common glass-blower's tube into a thin glass ball or bulb, about the size of a small hand-lamp shade, and the gasophaner is ready for use. When first made, the glass is clear, with beautiful iridescent colors, due partly to the thinness of its sides; but left for a time, shorter or longer, according to the amount of moisture in the atmosphere, in normal breathing air, it becomes covered or clouded with a light blue film (due chiefly to the carbonic acid gas of atmosphere), which, combined with the iridescent colors beneath, has an opaline or pearly luster. On bringing the clouded gasophaner carefully to the flame of a spirit lamp, this film instantaneously vanishes, leaving the glass of that part again clear and shining. The delicacy of this test is so great that, although by breathing on the newly-made gass, the film may be much more rapidly formed than by mere exposure to the atmosphere,an approach to the spirit lamp flame will no longer drive off the carbonated compound formed, on account of the impure gases contained in breath. At the same time, carbonates thus formed from the breath of a child, or of an extremely healthy person/vanish precisely as the aerial ones do on application of gentle heat. Held over a solution of ammonia,the air carbonate will not form, except on the upper part, where the ammoniacal gas I as less action; but if held so that the breath may mix withthe ammoniacal gas, a thick white cloud of carbonate of ammonia without opaline luster, covers the gasophaner. This cannot be driven off by heat, but froths up on an approach being made to the lamp flame. But the most remarkable indication given by the gasophaner is when it is held over a solution of sulphureted hydrogen. The gasophaner immediately becomes pitted, as it were, with small-pox, on the surface next the gas; and these spots, on being examined with a microscope, are found to be round radiated crystals, the center or nucleus of which soon bursts into a hole. They are white by transmitted and dark brown by reflected light. Nitride of boron gave exactly similar crystals as the chloride, and so did pure boracic acid. These crystals, therefore, are presumed to indicate a combination of boron with hydrogen a iact hitherto unknown to chemists. The gasophaner can be re-heated and re blown as often as required. American Locomotive Boilers. It is impossible, says Engineering, for an English engineer to read the records of American boiler explosions without being struck by the very large number of failures of locomotive boilers which "occur annually on the other side of the Atlantic. In this respect the American records form a strong contrast to those of explosions in this country. Here the number of locomotive boiler explosions seldom exceeds three or four per annum, and considering the large number of locomotives now at work in the United Kingdom, locomotive boilers may be said to possess a greater immunity from explosion than almost any other class. To a great extent, this is, no doubt,due to the fact, that locomotive boilers are, almost always, worked under skilled superintendence, and subject to frequent inspection ; but it is, also, due to their being, with but few exceptions, well constructed, in the first instance, and properly proportioned for the work they have to perform. In America, locomotive boilers, although under quite as skilled superintendence as our own,are yet more liable to explosion from the fact of their having generally less superfluous strength when new than would be considered necessary by our railway engineers. American locomotive superintendents use 5-16 and 3-8 inch plates, where we should use 7-16 or 1-2 inch ; and notwithstanding the high pressures used, double riveting is still the exception rather than the rule. The consequence of all this is, that in a list, now before us, of 94 boiler explosions which occurred in the United States during 1868, no less than 23 explosions of locomotive boilers are recorded, these explosions thus amounting to over 25 per cent of the whole ; while from another record of the explosions which took place in the month of May last, we find, that during that month four locomotives exploded on different American lines. These are facts which demand the serious consideration of American locomotive engineers, and we trust that in the records of future years we may find evidence that the lessons which they teaih have not been disregarded. A KEMAHKABLE statement has been made by Mr. Higson, the inspector appointed by the British Government, during the course of the inquiry into the Haydock calamity. He said that he " believed that half the explosions in Lancashire had taken place through the mere getting drunk of the miners over night.”