WARM CONTINUOUS MOIST STAGE 



345 



The stage A is placed in position on the instrument, and two 

 openings in this hollow stage at c d (A) are connected with two 

 similar openings in the water vessel, viz. g h (B). The whole is 

 carefully filled with water and raised to the required temperature 

 and regulated. 



The manner in which it accomplishes the end desired is as follows : 

 On the centre of the stage (A) will be seen a small cylinder of glass ; 

 this is ground at the end placed on the stage, and covered with a 

 sort of drumhead of indiarubber at the upper end. By examining 

 C with a lens it will be seen that a cell is countersunk into the 

 upper plate of the hollow stage at e", and a thin plate of glass is 

 cemented on to this. At e andtjjer disc of glass is cemented water- 

 tight, so that a film of warm water circulates between the upper and 



FIG. 298. 



under surfaces of this glass aperture. A glass cup is placed in the 

 jacketed receptacle f (A and C), and this also is filled with water. 

 A piece of linen is now laid on the stage (A, g) with an aperture cut in 

 its centre slightly less than the countersunk cell in which the glass 

 disc e" is fixed, and a flap from it is allowed to fall over into the glass 

 vessel f (A and C). Thus by capillarity the water is carried constantly 

 over the entire face of the linen. But the glass cylinder seen in A i& 

 made of a much larger aperture than the cell and the opening in the 

 linen, and consequently a large annulus of the linen is enclosed within 

 the cylinder. The drop of fluid to be examined is placed on the small 

 circular glass plate, and covered with the thinnest glass, the drum- 

 head cylinder is placed in position, the point of a high-power lens 

 is gently forced upon the top of the indiarubber through a small 



