ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 579 



the lateral eye-piece are mounted together on hinged bearings set in 

 such a position that the beam of doubly reflected light always occupies 

 the same position with reference to the axis of the lateral tube. By 

 turning the screw (fig. 56) the binocular tube is gently altered in its 

 angular position until the user's width of eyes is suited. If, then, it is 

 necessary to change the tube length, the inter-ocular distance can be at 

 once reset. In addition to the advantages already referred to, the makers 

 state the following :— 1. Suitability for all objectives from 1 in. to ^ in. 

 oil immersion, the full resolving power of every objective being retained. 

 2. Equal brilliance of image in both tubes. 3. Maintenance of defini- 

 tion so perfect that the interposition of the prism is unobservable. 

 4. Good range of tube length. 5. Production of stereoscopic or pseudo- 

 scopic effect at will by setting the interocular distance slightly narrower 

 or wider than the interpupillary distance of the observer. 



W. Watson and Sons' Agricultural Microscope.* — This Micro- 

 scope (fig. 58), has been designed specially for use in botanical and 

 agricultural work in which very low magnifications are frequently neces- 

 sary for the general examination of large specimens without loss of the 

 usual precision for medium and high-power observations. The coarse 

 adjustment, is W. Watson and Sons' regular spiral rack-and-pinion 

 pattern ; the fine adjustment being their standard lever form. The 

 important feature of the instrument is its very long range of coarse 

 adjustment which enables the highest and lowest power objectives to 

 be used with ample margin. This will be understood from the fact that 

 with an object 1^ in. thick laid on the stage, with a triple nose-piece in 

 position, a 3-in. objective of the parachromatic or Argus series will focus 

 with rackwork to span. The stage is of extra large size, 4f in. square. 

 AVhen the tube is racked down high powers such as -} in. or T ^ in. can 

 be employed. 



W. Watson and Sons' Grand Model Van Heurck Microscope 

 (1914 Model). f— The new model of this well-known instrument is 

 shown in fig. 59. It has been revised in several respects in order to 

 meet the demand for a long range of mechanical stage movement with 

 complete rotation at any position. The stage now has 2 in. of horizontal 

 traverse, and is fitted with movable object clips and removable spring 

 bar clips. The range in the vertical direction is about 1J in. The 

 milled heads work on one centre, and, if desired, can both be rotated 

 simultaneously, thereby affording a diagonal movement. The stage now 

 has a diameter of 5 in., and has complete concentric rotation. The 

 object is gripped by double sliding bars. It will be readily seen that 

 the altered shape of the limb gives great freedom to the surface and, 

 incidentally, acts as a convenient handle. 



* Catalogue, " Microscopes and their Accessories," W. Watson & Sons, London 

 (1914-15) pp. 34-5. 



t Catalogue. " Microscopes and their Accessories," W. Watson & Sons, London 

 (1914-15) pp. 74-5. 



2 Q 2 



