A PLUMBING TEST.

A recent trial of a smoke rocket for testing drains, described by Mr. Cosmo Jones in the Journal of the Society of Arts, is deserving of interest.  The one fixed upon is 10 in. long, 21/2 in. in diameter, and with the composition “charged rather hard,” so as to burn for ten minutes.  This gives the engineer time to light the fuse, insert the rocket in the drain, insert a plug behind it, and walk through the house to see if the smoke escapes into it at any point, finishing on the roof, where he finds the smoke issuing in volumes from the ventilating pipes.  The house experimented upon had three ventilating pipes, and the smoke issued in dense masses from each of them, but did not escape anywhere into the house, showing that the pipes were sound.  If the engineer wishes to increase the severity of the test, he throws a wet cloth over the top of the ventilating pipe, and so gets a slight pressure of smoke inside it.

* * * * *

THE GAS ENGINE.[1]

[Footnote 1:  Lecture by Mr. Dugald Clerk, before the Literary and Philosophical Society, Oldham.]

By Dugald Clerk.

In earlier days of mechanics, before the work of the great Scottish engineer, James Watt, the crude steam engines of the time were known as “fire engines,” not in the sense in which we now apply the term to machines for the extinguishing of fires, but as indicating the source from which the power was derived, motive power engines deriving their vitality and strength from fire.  The modern name—­steam engine—­to some extent is a misleading one, distracting the mind from the source of power to the medium which conveys the power.  Similarly the name “Gas Engine” masks the fact of the motors so called being really fire or heat engines.

The gas engine is more emphatically a “fire engine” than ever the steam engine has been.  In it the fire is not tamed or diluted by indirect contact with water, but it is used direct; the fire, instead of being kept to the boiler room, is introduced direct into the motor cylinder of the engine.  This at first sight looks very absurd and impracticable; difficulties at once become apparent of so overwhelming a nature that the problem seems almost an impossible one; yet this is what has been successfully accomplished in the gas engine.  Engineers accustomed to the construction of steam engines would not many years ago have considered any one proposing such a thing as having taken leave of his senses.

The late Sir William Siemens worked for many years on combustion engines, some of his patents on this subject dating back to 1860.  In the course of a conversation I had with him on the subject of his earlier patents, I asked him why he had entitled one of those patents “steam engine improvements” when it was wholly concerned with a gas engine using hydrogen and air in the motive cylinder, the combustion of the hydrogen taking place in the motive cylinder.  He answered me that in 1860 he did not care to entitle his patent gas or combustion engine simply because engineers at that time would have thought him mad.