866 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
simultaneously rotated while the stage remains fixed. The apparatus, 
which is represented in fig. 97, is carried by a support T attached by the 
screw s to the fine-adjustment column of the Microscope. On the end of 
the support rises a hollow column S, terminated by a hollow axis which 
carries the burner B B'. The latter can be brought into the vertical 
position, which is shown dotted in the figure, by means of the handle < 7 , 
and it is always in this position that the crystal is heated. The gas 
Fig. 07 . 
brought by the tube G passes through the cock H into the column, and 
thence through the axis to the burner B. At the foot of the column are 
holes for the admittance of air, which can be regulated by means of a 
second cock h'. The arrangement of the crystal holder is somewhat 
similar to that adopted in the second apparatus. As in that arrangement 
the crystal is held between two pieces of platinum foil, the middle por- 
tions of which form square plates, pierced by central apertures. From the 
square central part of one of these plates there project on each side two 
arms, the ends of which are riveted to the under surface of the steel rods 
o o'. From the middle part of the second plate two arms project between 
the arms of the first plate, and are riveted to the upper surface of the steel 
rods. The arms of the two plates are thus separated by the thickness 
