112 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



from friction, as there are no metal surfaces in contact ; the only- 

 friction is between the point of the screw at P, where it acts on the 

 bar by pressure. The suspension of the optical body is strictly on 

 the two springs C C. The open space shown at G is free from all 



contact of the metal faces. The metal plates used on both sides to 

 cover up the mechanism in the limb (removed from the side in our 

 figure to enable the construction to be seen) do not touch the moving 

 surfaces. 



It may also .be noted as a novelty that the axis and foot of the 

 Microscope are marked so as to indicate the proper degree of inclina- 

 tion required to place the camera lucida 10 inches above the table. 



(2) Investigator. The general form of this instrument sufficiently 

 appears from Fig. 6. The main tube has two draw-tubes, which is 

 claimed to be an " entirely new feature in Microscopes, and an un- 

 questionable improvement. It permits the use of the standard length 

 of tube for quick adjustment in outside tube, the same as in instru- 

 ments without rack and pinion adjustment ; it serves also for any low- 

 power objective, and the amplifier can be used in either combination. 

 The outside tube has a broad-gauge screw, and an adapter with the 



* The double draw- tube was adopted in a " revolving "- body Microscope 

 constructed by Mr. Browning in 1873; it was figured in the Montli. Micr. 

 Journ., X. (1873) p. 234. 



