Processes in the Useful Arts. 151 



triangle were of equal length,) but is taken from a triangle executed for the 

 police establishment of this city. 



4. Account of an improved Hydropneumatic Lamp, which can be construct- 

 ed at a small expence. By William Dyce, M. D. F. R. S. Edin. 



This lamp consists of a cylindrical glass jar, open at the top, A B Plate 1. 

 Fig. 6. ; into this jar is placed a bottle, C D, of the same kind of glass, which 

 nearly fills it in point of circumference. With respect to the inner.bottle, it is 

 to be cut in two, so that when placed again in the outer jar, it only occu- 

 pies one-half its space in altitude, which space, however, must be made up 

 by means of a piece of leaden pipe, E F, of such size as will easily grind 

 into the neck of the bottle, projecting, at the same time, about an inch 

 above the upper part of the outer jar, which passes through an opening 

 in the centre of a covering of mahogany, turned for that purpose. Into 

 the upper part of the leaden tube is ground a small brass cock F, which 

 can be procured from braziers at from 10d- to 14d., according to the size. 

 Now the upper part, or that from which a fluid would flow, is to be filed 

 or cut away, so as to admit of a piece of brass tube, about | of an inch in 

 diameter and £ in length, being soldered to the nozle, into which is fitted 

 a piece of glass tube, drawn into a point, and bent downwards so as to be 

 parallel with the stem, and, of course, to blow downwards, whereby the 

 stream of hydrogen gas is directed upon the spongy platinum in a small 

 box, G, moveable up and down through the wooden cover, by a spring- 

 tube made fast to the cover ; at the same time that this small box has a 

 cover or top fitted to it, and easily moveable by means of a joint, so as to 

 be accessible in darkness as well as light. 



Every person knows, that rags on being burnt, so as to be in a com- 

 plete state of incandescence without flame, are fit for tinder, and that 

 this tinder may be inflamed by a spark, nearly as soon as gun-powder. 

 Now, if these rags, of which the tinder is to be made, be immersed in 

 the solution of platinum, dried and then burnt, the product will answer 

 quite as well as Dr Fyfe's instrument for inflaming sulphur. On most oc- 

 casions, indeed, it will inflame the gas without any farther trouble, yet, it 

 must be allowed, at a much greater expence of gas before the inflammation 

 takes place ; but if the tinder only is required to be set on fire, then a very 

 small portion of gas will be needful for that purpose, and a common brim- 

 stone match will produce the flame required. On certain occasions, I have 

 found this method preferable to the spongy platinum when the column of 

 water was not of sufficient altitude to force out the gas with sufficient ra- 

 pidity to be inflamed, and yet was quite equal to the inflammation of the 

 tinder, from which a match could be lighted, and that without any hurry, 

 as it keeps ignited for a very long time. 



In like manner, common charcoal answers the same purpose. If any 

 quantity of powdered, fresh made, charcoal be moistened with the solution, 

 and then submitted to a red heat, or nearly so, it possesses the power of 

 inflaming the gas, if a jet be directed to it for a considerable length <>(' 



