586 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
opening in the standard H. On the fine adjustment slide F rests, very 
solidly screwed, the gear P for the coarse movement. The aluminium 
tube T (fig. 90), in order to avoid undue wear and tear of the mechanism, 
Fig. 101 . 
is connected in the usual way with the tooth-rack by means of a copper 
companion piece Z (fig. 100). The coarse adjustment follows the usual 
models. The micrometer-screw is thus seen to be packed away in the 
