558 



SUMMARY OF CURRENT RESEARCH i;s. 



Watson's Research Microscope. * — The general design of this 

 Microscope (fig. 97) conforms to that of others by the same manu- 

 facturers. There are, however, some changes in the details. The fine 

 adjustment is set at the side of the limb, and operates a lever set 

 vertically. A complete turn of the milled head imparts a movement to 

 the fine adjustment of • 1 m/m. It will be observed from the figure 

 that the stage is made" on the Tyrrell system, with the milled heads 

 working through one another. The horizontal traverse given by the 

 screw is If in. The method of attachment of its stage differs from the 

 usual — the limb is continued beneath the stage, and projects forward 

 so as to form a shelf to which the base of the stage is screwed ; a hollow 

 is formed between this shelf and the lower portion of the limb by 

 machining away a portion of the exact thickness of the stage-plate. 

 When, therefore, the stage is mounted on the shelf previously referred 



Fig. 98. 



to. it is further gripped from the top by a fitting portion of the hmlj, 

 and an unusually rigid attachment is secured by this means. A long 

 range of coarse adjustment is given to the body, so that very low-power 

 objectives can be used when occasion requires. 



(2) Eye-pieces and Objectives. 



New Holoscopic Eye-pieces. f — The Holoscopic Eye-pieces (fig. 98) 

 by W. Watson and Sous, Ltd., have been re-computed, and are now made 

 with an achromatic eye-lens whereby the eye-point is lengthened. The 

 convenience of an adjustable fitting so that they may be used either 

 for apochromatic or achromatic objectives is still preserved, and their 

 construction has been so framed that they materially counteract the 

 want of flatness of field which is inevitable in high power objectives. 



* Catalogue, 1912-13, p. 51. 



t Watson and Sons' Catalogue, 1912-13, p 96, 



