On the Steam Calorimeter. 



235 



mean temperature of the body if a bad conductor. I take the last if 

 a good conductor. In any case the error introduced will be small, 

 but, of course, it is to be avoided. 



It is seen in section that the calorimeter is double walled. The 

 carrier and catchwater are shown hanging within it. In form it is 

 cylindrical, the inner cylinder being cone-shaped at each end. The 

 pitch of the upper cone is made so high that drops of water will run 

 down it, and not fall off it. It is of brass, very thin, the inside being 

 gilt and burnished. This is not essential, but keeps it very clean 

 from the sulphur and antimony which are carried from the rubber 

 steam-pipe by the steam. The surfaces between the walls are simply 

 burnished. Outside it is covered with well-shrunken cloth. The 

 steam admission way is in the upper part of the calorimeter, and by 

 this pipe this upper part is securely fixed to the upright supporting 

 the table carrying the balance. The lower part is entirely removable 

 from the upper. It meets it on a well-ground surface, and is secured 

 in its place by an external bayonet catch at either side. Steam is 

 admitted by the brass pipe shown in position at the other side of the 

 upright. This pipe is removable and is very readily laid in its place, 

 being guided by a hollowed-out wooden support attached to the base 

 boaru of the calorimeter-stand. It is connected by a thick rubber 

 tube, 24 cm. in internal diameter, with the boiler. This tube must 

 have a fall the whole way to the boiler to keep it from choking with 

 water. On steam being admitted, it rapidly drives out the air, the 

 steam descending in the calorimeter. To allow the air to escape, a 

 means is provided for opening the lower orifice of the calorimeter 

 fully. This is effected by rotating a milled-headed screw projecting 

 at the side of the stand, and shown dotted in the section. The 

 shaft from this screw passes across the face of the upright board 

 carrying the calorimeter, and is furnished with two projecting arms. 

 One of these is provided at its extremity with a hard-wood cup, 

 shown dotted, in the depressed position. The other carries a conical 

 catchwater of brass with a sloped brass tube attached, shown in 

 position at the lower orifice of the calorimeter. Either of these, the 

 wooden cup, or the cone and tube, may be brought to cover the 

 orifice in the calorimeter by a longitudinal movement (of about 

 25 cm.) of the shaft of the milled-headed screw. Before experiment 

 the non-conducting wooden cup closes the orifice. Just before 

 coupling with the boiler, this is depressed and pushed back. When 

 it is judged from the appearance of the steam escaping at the orifice 

 that all air is expelled, the cone and tube are elevated against the 

 orifice, closing it except for a slow current of steam still free to issue 

 from the sloped tube. The water draining from the calorimeter also 

 issues through this tube, falling into a dish placed to receive it. 



The thermometer for reading the initial temperature is inserted in 



