1818.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



3-9 



which he teaches. It is in these qualities th;it consists the use for 

 the professional man, who is able practically to supjily the de- 

 tailed information, and may refresh his memory by reading, under 

 each head, the enumeration of the various resources applicable to 

 the work intended. 



HYDROGEN GAS AS A MOTIVE POWER. 



Among the patents for new inventions in this country specified 

 within the last month, is one (obtained by the widow of a French 

 engineer, at the request of her late husband,) for employing the 

 explosive force of hydrogen gas as a motive power. In the arrange- 

 ments for ett'ecting this object there is nothing deserving of special 

 notice, the explosive force being made to act against pistons work- 

 ing in two cylinders, wherein the explosions of the gas mixed with 

 atmospheric air take place alternatelj', either by the agency of 

 electricity or by the flame of a gas-light. To what extent how- 

 ever sucii an explosive force would be available, supposing it could 

 be regulated to act with uniform pressure, is a question deser\ing 

 consideration, as the attempt has been previously made, and may 

 be again and again repeated. 



There is a peculiarity in the power generated by all explosions, 

 which renders it almost impossible to employ it usefully in working 

 machinery; inasmuch as the greatest part of the force exerted de- 

 pends on the instantaneous or percussive action, which enables it 

 to overcome resistances that would not yield to the same amount 

 of force steadily applied. In the explosion of hydrogen gas there 

 is the further peculiarity, that the resulting product occupies so 

 much less space than the original gases as to result in a partial 

 vacuum ; and we have heard a popular lecturer when noticing 

 this result assert, that in such explosions the force is directed 

 altogether inwards, and that there is no external force whatever : 

 this assertion, too, was made in defiance of the common experi- 

 ment of the electrical pistol, w ith which he must have been fami- 

 liar. The external force is indeed only momentary, and depends 

 upon the instantaneous expansion of the gases by the heat caused 

 by their ignition ; consequently, the difficulty of regulating such a 

 power is greatly increased ; but that there is power exerted there 

 can be no doubt, though the amount of it we believe to be too 

 small to be ever practically available. 



VVith a view to ascertain the amount of force generated by the 

 explosion of hydrogen gas, we some years since made several expe- 

 riments, which, if not strictly accurate, were sufficiently so to 

 enable us to conclude that the force generated is much too small 

 to be of use, and amounts only to the expansion of the gases em- 

 ployed into about eight times their original volume; or to the 

 exertion of a momentary pressure of eight atmospheres. The ex- 

 periments were arranged in two different ways, but the results 

 nearly coincided. The first method adopted was, to ascertain the 

 quantity of water displaced by the explosion of a given volume of 

 hydrogen gas mixed with atmospheric air. A square tin vessel, 

 open at the bottom, w as made ; to the top of which there was sol- 

 dered a smaller tin vessel that held one cubic inch. This smaller 

 vessel for holding the gas, was open entirely at the bottom, so as 

 to form in fact only a projection from the top of the larger one. 

 Insulated wires were introduced into the small gas-holder, for the 

 purpose of causing explosion by means of an electric spark. The 

 vessel having been filled with and inverted in water, a cubic inch 

 of an explosive mixtKre of hydi'ogen gas and atmospheric air was 

 passed up into the small reservoir. A small trough, into which the 

 tin vessel was inverted, was then filled exactly to the brim; and the 

 tin was held firmly on supports, which raised it several inches 

 above the bottom of the trough. The electric spark was passed 

 through the gas, and the explosion forced over a quantity of water 

 into a receiver. By measuring the water thus displaced, the ex- 

 pansion of the gas by heat during the explosion was ascertained. 

 This experiment was several times repeated with nearly corre- 

 sponding results : the amount of water displaced being about eight 

 times the volume of the mixed gas. 



In the second method the experiments were made in the dry way. 

 Under the impression that the explosive force was very great, a gun 

 barrel was procured ; and a piston, attached to a small rod, was 

 loosely fitted into the barrel. The mixed gases were introduced 

 from a bladder through a hole at the breach ; the space occupied by 

 the gases being measured by the height to which the piston was 

 drawn up. Tlie explosion of the gases was effected by an electric 

 spark: and the space in the gun-barrel through which the piston 

 was forced was ascertained by a narrow ribbon attached to the 

 piston rod ; the ribbon being drawn out with the rod during the ex- 



plosion, and left loose afterwards. The loose part of the ribbon 

 indicated the extent to which the piston had been forced from its 

 first position, and by measuring and comparing it with the space 

 of cupied by the gas, the expansive force of the explosion was de- 

 termined, and it nearly agreed with the results of the first set of 

 experiments. In the course of these experiments the operator had, 

 unexpectedly, personal experience of the force exerted by tlie 

 explosion. The bladder containing the mixed gases, whilst held 

 under his arm, was inadvertently brought near the flame of a 

 candle, and the contents exploded' with a loud report and concus- 

 sion, that blew out the candles and left him in the dark, somewhat 

 stunned, indeed, by the force, but without inflicting any injury. 



Though these modes of experimenting were certainly not calcu- 

 lated to afiord very accurate results, yet they proved that the ex- 

 pansi^■e force of hydrogen gas is \ery much less than we had antici- 

 pated, and that consequently it was useless to pursue our attempts 

 to render it a\'ailable as a motive power. It is very probable that, by 

 using other proportions of hydrogen gas and atmospheric air than 

 we employed, greater force may be obtained; but it cannot, we feel 

 convinced, be under any circumstances at all comparable to the 

 explosi\'e force of gunpowder. The terrific effects so frequently 

 produced in coal mines by explosions of carburetted hydrogen 

 gas, may probably lead to the supposition that the explosive force 

 is immense ; but if the large volumes of gas exploded in producing 

 such disastrous results be taken into consideration, it will be found 

 that the power exerted is insignificant, compared with the explo- 

 sive force of other agents. 



NEW ELECTRIC LIGHT. 



An experiment was made on the Great Western Railway, on the 

 18th ult., to test the power of a new species of light produced by 

 electricity, particularly with a view to its being used by railway 

 trains. The light is produced by an apparatus invented by M. Le 

 Mott, a French gentloman, who has been for several years em- 

 plo} ed in electrical experiments in Russia, and whose discoveries 

 in that department are well known to the scientific world. At half- 

 past six o'clock a truck, containing a square wooden box, about the 

 size, though not the shape, of a sentry-box, and having a galvanic 

 battery of some 60 or 70 small jars disposed around it, was attached 

 to the last carriage of the tiain then about to proceed from Pad- 

 dington. The light was produced inside the box, and the rays, 

 condensed and heightened by a powerful reflector, were emitted by 

 an aperture contrived for the purpose. The light was produced 

 before the train left Paddington, when a dazzling blaze filled the 

 whole of the spacious station, casting the numerous gas lamps 

 there completely into the shade. As the train proceeded on its 

 way, the reflection left a long track of clear bright light for the 

 distance of a mile and more behind it, in such a manner as to ren- 

 der it utterly impossible that any train coming up behind should 

 run into it, except as the effect of deliberate intention. The re- 

 flection, as seen from the carriage, was very beautiful, the pris- 

 matic colours being distinctly and vividly delineated along the 

 outer edge of the circle of radiation; and as these fell upi^n the 

 dense column of smoke ascending from the engine, the effect was 

 singulai and striking. The night was dark, but clear, and so far 

 favourable to the experiment ; and objects, such as a bridge, were 

 rendered distinctly visible at the distance of about two miles. The 

 experiment was made as far as Slough, on arri\'ing at which station 

 the truck was detaclied from the train, and continued there for 

 about half-an-hoiu', till the up-train arri\ed, with which it returned 

 to town. While at Slough, the light was turned in the direction 

 of Windsor Castle, as it was the expectation of M. Le Mott, 

 who accompanied the experiment, that it would be seen from 

 thence. While there a gentleman stationed himself at the dis- 

 tance of 200 yards or so from the apparatus, and read a newspaper 

 by the light produced, which he found he could do with perfect 

 ease. Tlie apparatus then returned to town in the same manner, 

 the light being continuously intense during the whole of the jour- 

 ney and return ; and we were informed by the ingenious inventor 

 that thei'e could be no diflSculty in keeping it up for the whole 

 night. The experiment afforded great satisfaction to all who wit- 

 nessed it, the only drawback being, that the apparatus, having 

 been in the first instance adapted for stationary e.xperiments, suf- 

 fered considerably from the jolting- inseparable from railway mo- 

 tion — a defect which the inventor considered might be with ease 

 overcome in any future experiment. 



