in use, snch as Strieker's, described by Klein in Sanderson's Hand 

 Book, to be clumsy and difficult to manage with precision, has 

 contrived an apparatus which is moderately easy to prepare and 

 use, and extremely precise in its results. It consists essentially 

 of three parts, the stage, the hot-water reservoir, and the gas 



The stage is a hollow brass-box, closed at every point except an 

 inlet pipe at one end and an outlet pipe at the other. Through 

 the centre of the stage is an opening or centre chamber for the 

 transmission of light through the object. This chamber is closed 

 above and below with cover-glasses, upon the upper of which the 

 object rests. It communicates with the external air by a hori- 

 zontal tubular opening through which a thermometer may be in- 

 troduced to test temperature, or tubes for the introduction of 

 gases or other reagents, but has no communication with the gen- 

 eral cavity of the stage. 



The reservoir consists of a vertical brass cylinder, containing 

 hot water, which is heated by a gas flame below. From the top of 

 this reservoir the hot water passes with a slight ascent through a 

 flexible rubber tube to one end of the stage, through the length of 

 the stage and back by a descending course through a rubber tube 

 to the bottom of the reservoir. This is a closed circuit entirely 

 filled with water, the hot water rising on one side and the cooled 

 water falling on the other, precisely as the water pipes in the 

 kitchen stove or range heat the copper boiler which supplies the 

 hot water pipes of our houses. The reservoir is made hollow for 

 the reception of the gas regulator. 



The gas regulator is not unlike a thermometer with the top of 

 the tube broken off. A steel tube with a narrow slit in one side is 

 cemented tightly into the top of the glass tube of the regulator, 

 and delivers the gas inside of the glass tube .and some distance 

 below its upper end. The glass tube has a side opening above the 

 level of the bottom of the steel tube, from which the gas is carried 

 by a flexible tube to the burner beneath the reservoir. The regu- 

 lator is filled with mercury which, when the required temperature 

 has been attained, is adjusted so as to just touch the bottom of 

 the steel tube, the flame below the reservoir being only preserved 

 by the gas which escapes through the slit in the steel tube, but the 



