IV. CALORIMETKY. 269 



chamber. The stopper is formed of a piece of metal exactly fitting the upper 

 part of the combustion chamber, and carrying two tubes, by one of which can 

 be introduced the pipes for hydrogen or oxygen according to the nature of the 

 combustion desired. The other is used for watching the combustion. For 

 that purpose it is closed at its lower end by a threefold plate, of glass, quartz, 

 and alum ; a small looking-glass is placed at the upper end of this tube, and by 

 this means all that is going on in the interior can be seen. 



lO58b. Regnault's Apparatus for determining Specific 

 Heat of Gas. L. Golaz, Paris. 



This apparatus, constructed for M. Regnault by the exhibitor, consists of 

 three parts: 



1. This affords the means of obtaining a current of gas, the velocity of 

 which is constant and can be regulated as desired. 



2. The bath, which imparts a determinate initial temperature to the gas. 



3. The calorimeter in which the gas parts with its excess of heat. 



The first part of the apparatus is composed of a copper reservoir, holding 

 about 35 litres, and provided with two stop-cocks. It is placed in a vessel 

 filled with water, which keeps it at a temperature sensibly constant, and 

 always accurately known. The central reservoir is full of gas under a pressure 

 determined by a syphon pressure gauge. 



The flow of the gas is regulated by a delicate valve formed of a vertical 

 tube, in which a close fitting spindle works by means of a micrometer screw. 

 The end of the spindle is conical, and fits into a corresponding seating at the 

 bottom of the tube. The diameter of the spindle is slightly diminished about 

 one centimeter above the cone. The gas passes into the valve through a 

 capillary opening at the apex of the conical seating, and passes out round the 

 diminished part of the spindle to the outlet pipe, which is about a centimeter 

 above the inlet. In connexion with the outlet pipe is a syphon pressure 

 gauge. The amount of clearance given to the valve is indicated by a 

 graduated disc fitted to the top of the spindle. 



The oil-bath which heats the current of gas consists of a cylindrical vessel, 

 in which is a helical tube ten metres in length. Its extremity is connected 

 with the calorimeter by means of a nozzle, in which is fitted a small tapering 

 glass tube by means of a cork, through which it passes. The bath has a cover 

 at the top, through the middle of which passes a square rod carrying an 

 agitator ; a short tube fixed to the cover, near the exit of the gas, allows of 

 the introduction of a thermometer, so that the temperature of the gas before 

 entering the calorimeter can be ascertained. 



The boiler is preserved from immediate contact with the surrounding air 

 by means of a metallic jacket, which serves at the same time as a support ; 

 the base of this support is furnished with levelling screws ; an iron column 

 placed behind supports a rod with a clamp holding a horizontal bar, at the 

 end of which is a pulley over which passes the cord sustaining the agitator. 

 The bath is warmed by a gas lamp. 



On leaving the bath, the gas goes into the calorimeter, which consists of a 

 cylindrical vessel of thin brass, provided with a nozzle through which the 

 gas enters, and 4 shallow cylindrical boxes, through all of which the gas 

 passes successively. These boxes communicate with one another and with the 

 lower vessel by means of tubes suitably arranged ; on leaving the uppermost 

 box, the gas discharges itself into the atmosphere by a short tube. A very 

 thin strip of brass bent spirally is in the interior of each box ; so that the gas 

 on leaving the principal vessel traverses successively the superposed boxes, 

 circulating the while for a long time in contact with their cold sides and in 

 the ducts which offer sections sufficiently large for resistance to be but very 



