102 SUMMARY OF CURRENT RESEARCHES RELATING TO 



limb of the Microscope is fixed bj means of a screw-clamp. The limb 

 IS round and hollow, and contains a triangular bar, upon the posterior 

 edge ot which the coarse-rack is cut ; on the top of this bar a short curved 

 arm is fixed by means of a screw, about which the arm can be rotated 



FiQ. 8. 



and screwed in any position. The body screws on to this arm ; it is 



tZ'.. X f T'? "" Huyghenian eye-piece with two plano-convex 



model' of 18?r ^T^^'r^ f ^'"^ P'""^^'^ ^'^ '' present in the later 

 moael ot 1838). The hmb carries the concave mirror andi also a 



