16 THE PRESIDENT'S ADDRESS. 



traduction been improved by bringing the friction wheels 

 nearer together, and also by fixing a milled head to each 

 end of the pinion for the horizontal movement. This stage 

 secures a maximum range of motion in each direction, and 

 at the same time the whole apparatus can be removed, leaving 

 the main stage perfectly plain. A copper ring is swedged on 

 the wheels which impart the horizontal movement to 

 the slide, and corundum powder is rubbed into it, which 

 increases the grip on the lower edge of the slide. Next 

 we have a series of microscopes, exhibited here by Messrs. 

 Ross ; they do not materially differ from the ordinary Anglo- 

 Continental pattern of students' microscopes except in the 

 foot. The limb is fixed by a compass joint to a pillar which is 

 attached to the periphery of a circular foot ; so far they are not 

 unlike Salmon's microscope (1853) described by Dr. Beale. 

 This pillar is, however, pivotted so that the foot may be turned 

 backwards, which gives great steadiness to the instrument 

 when in an inclined or horizontal position. This forms a 

 simple, inexpensive and thoroughly practical foot, and it is 

 strange that such an efficient design has not been oftener 

 employed in the construction of students' microscopes. This 

 idea was first suggested by Mr. A. McLaren.* 



We next come to Baker's photomicrographic instrument. 

 Here we have a microscope which cannot be used in any other 

 but the horizontal position. The focussing racks of the body 

 and substage are all ploughed in the bedplate, and the foot and 

 arm are dispensed with. This seems to me the most solidly- 

 e< instructed photomicrographic instrument yet made. This 

 excellent design is due to Mr. E. Hartley Turner, of Man- 

 chester. It is an instrument that will be much appreciated by 

 those who do all their microscopical work on the photographic 

 bench. Personally I work on different lines, the magnification, 

 lens, adjustment, illumination, position, etc., of the object being 

 all determined before it is placed on the photographic bench, so 

 1 naturally prefer to photograph with the same instrument by 

 which those adjustments were made, and would find some 

 inconvenience in changing to another instrument; but this is a 

 mere raa1 fcer of detail. 



The Last microscope is Watson's new model Van Heurck. 



* "Journal It. M. 8.," 1884, p. J 11, Pig. 9. 



