The Eolipile, fig. 11., Plate XXXIV. has been ap plied to act as a blow-pipe. It is a hollow vessel of brass, sometimes made in form of a smelt kettle, some times in form of a ball of two inches in diameter, with a tube of brass that screws into IL The tube is to be screwed off in order to pour in alcohol by a small funnel; and then the tube being replaced, and heat ap plied to the bulb, the vapour of the alcohol issues from the small apertureof the tube, and being directed' against the flame of a lamp, the flame is driven in a horizontal stream, such as the blow-pipe produces. The instrument has a safety-valve (S) to prevent the danger_ of explosion, which might happen if the noale were stopped. The same wick that heats the bulb may serve to furnish the jet of flame, as is the case in the eolipile represented in fig. 11. This in strument has been proposed to be applied to the par poses of the mineralogist; but it does not appear to be either so readily put in action, or so efficacious as the common Wow-pipe, which is also simpler in its construction, less bulky, and more easily carried about.
Mr Newman, philosophical instrument maker of Lisle Street, London, having observed that air, con densed in a cavity, required a considerable time to escape through a small aperture made to give it contrived the apparatus represented at fig. 12., which acts as a blow-pipe. This apparatus consists of a strong plate copper box perfectly air-tight, three inches in width and height, and four in length, a con densing syringe to force air into the box, and an ad jutage with a stop-cock at one end of the box, by which the issue of the air is regulated. The piston rod of the condensing syringe works through collars of leather in the cap, which has an aperture in the side, and a screw (N) connected with a stop-cock, which may be made to communicate with a jar, bladder, or gazometer, containing oxygen, hydrogen, or other gases. When this communication is made, and the condenser worked, the gas contained in the jar or bladder is thrown into the box, and issues through the adjutage upon the flame of a lamp placed near it. • When the apparatus is worked with common air, a few strokes of the piston fills the chamber with compressed, air. When the cock of the adjutage is opened, the air issues with great ve locity in a small stream, and when directed on the flame of.,a lamp, produces a jet of flame as the com mon blow-pipe does, but with more precision and re gularity. The force of the stream of air is easily adjusted by opening more or less the stop-cock of the adjutage • and, when the box has been mode rately charged, the stream will continue to issue uni formly for twenty minutes; when the strength of the blast begins to decline, it will be restored by work ing the syringe. The apparatus is very portable, and
not liable to injury. It is made by Mr Newman, the inventor, with a lamp adapted to it, so as to pack up in a box not more than six inches in length, and four inches in width and height, enough of space being left for other small articles : others he makes in boxes somewhat larger, so as to contain also a selection of chemical tests. See Journal of Science, edited at the Royal Institution, No. 1.
Sir Humphrey Davy having discovered that the ex plosion from oxygen and hydrogen gases would not communicate through very small apertures, Mr Chil dren proposed to him to employ Newman's blow-pipe foreffecting a combustion of a mixture of oxygen and hydrogen gas, issuing from a small aperture. This Sir Humphrey did, and found that the flame pro duced the most intense heat, which instantly fused bo dies of a very refractory nature. Dr Clarke, Professor of Mineralogy at Cambridge, having consulted Sir Humphrey on the subject, proceeded to expose a great variety of mineral substances to the flame, for the purpose of observing its effects upon each of them. The tube of glass through which the mixture of the two gases is to issue, is cemented on the pipe of issue of Newman's blow-pipe. The tube at first used by Dr Clarke was 3 inches in length, and the dia meter of its cavity nth of an inch. The end of the tube was constantly breaking during the experiments owing to the sudden changes of temperature, until at last he usually worked with a tube only one inch and three-eighths in length. When the current of gas- is feeble, from the gas in the reservoir having come nearly to the same degree of density as the surrounding air, or from the current being suppres sed in the beginning of an experiment, then the flame has a retrograde movement, passing up the ca pillary cavity of the tube about half an inch, and, after splitting the end of the glass tube, the flame goes out of itself; so that, even in this case, there is no danger of explosion. In order to try the ef fects of an explosion, four pints of a mixture of the two gases were condensed into the chest, which was all that the syringe could force into it. The glass tube was taken off, so that the diameter of the nose pipe, by which the gas was to issue, was about one eighth of an inch. A burning spirit-lamp was placed at this aperture, and the stop-cock being opened by means of a long string attached to it, the whole gas exploded with a report like that of a cannon ; the chest was burst, the stop-cock driven out, and one end of the chest was torn off and thrown against the wall of the room. This shows the danger of using the apparatus with too large an aperture, and the necessity of employing a capillary tube.