84 REPORT — 1844. 



secured pass under the inclined planes of two corresponding wedges screwed 

 to the brass plate. By this contrivance, due to the ingenuity of Mr. Bryan 

 Donkin, jun., a quarter of a turn of the stopper suifices to secure the joint, 

 which is afterwards at leisure more tightly fastened down by two additional 

 screws. 



The aperture in the brass plate gives admission to a colander of the same 

 length as the tube, made of copper, and designed to hold the charge of zinc. 



A conducting pipe of copper tubing connects, by means of union-joints, 

 the tubulated stopper with a brass stand, in which is a chamber where the ga.s 

 is cleansed after having been partially dried by sponge introduced into the 

 cavities of the stopper. In this chamber a glass vessel is placed which con- 

 tains absorbent materials, and to the bottom of which the gas is conveyed by 

 a tube. 



With the chamber are connected by similar copper tubing two supports 

 for burners, the supply of gas to which is commanded by two stop- cocks 

 attached to the chamber, so that they may be employed either separately or 

 together. 



I have contrived various forms of burners for different purposes : that which 

 is best adapted for concentrating heat is a truncated brass cone ground within 

 another cone, and inscribed on its face with lines converging to the axis. But 

 for the purpose of bringing a vessel to an uniform temperature, the jets of 

 flame must be directed in the manner best fitted to distribute the heat : a 

 fine jet of hydrogen issuing with such force as to create a strong current of 

 air, and thus blow, as it were, its own bellows, produces very intense heat, a 

 heat so intense that I have fused with it at high pressures hyacinths and jar- 

 goons : even at the lower pressure, which I am now going to use, vessels of 

 platina are liable to be melted at the extremities of the jets, whilst at the 

 intervals between them the metal is far below the point of fusion. I deter- 

 mined, therefore, to attempt to equalise the temperature by giving the vessels 

 a rotatory motion, so that the jets of flame might act on successive points at 

 successive moments ; and I arranged the jets in spirals, flat or elevated, as 

 dishes and crucibles of different forms required, so that each jet should de- 

 scribe a separate circle on the surface revolving before its point, and that 

 those circles should be equally distributed over the surface of the vessel : the 

 burners are copper tubes twisted into the required forms, and furnished with 

 nipples tipped with platina, finely bored, and screwed into the tube. By this 

 arrangement the currents of air pass uninterrupted, the tubes are not in 

 danger of being fused, and the number of jets may be regulated by plugging 

 more or fewer of the apertures within the screws. To effect the rotation, I 

 adapted a watch-movement to the wires from which the crucibles depend ; 

 and, at Mr. Donkin's suggestion, I use for the same purpose a light fan, which 

 is moved by the heat of the burner : for low heats this does not answer so 

 ■well as the watch-movement, but at high temperatures it has the advantage of 

 increasing the velocity of the rotation in proportion to the intensity of the heat. 



Another copper pipe, connecting by union-joints the chamber Avith agauge, 

 completes the apparatus. The gauge consists of a double iron chamber con- 

 taining mercury; into the upper part of the inner chamber a strong glass 

 tube is secured by leaden washers and a perforated screw : the graduations 

 of the tube begin with eight atmospheres and are carried to 150. 



On the present occasion I intend to employ a quantity of gas, which, if 

 liberated at once, would give a pressure of about 6G atmospheres, but at the 

 rate at which it is actually formed will in ten minutes give about one-third . 

 of that pressure. For this purpose I have poured into the generating tube 

 \0\ pints of water and f of a pint of oil of vitriol, and have allowed the mix- 

 ture to cool. I now introduce the colander, into which I have put 15 ounces 



