ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



803 



from the mirror obtained at once. Fig. 100 is view of the under side, 

 and shows the way in which it is done. This is a distinct advantage, 

 and workers with the ordinary form of instrument, in which the con- 



FiG. 100. 



denser must be withdrawn if direct light from the mirror is required, 

 will at once appreciate it. The stage of the instrument is 3^ in. 

 square, permitting of the use of large slips. The eye-pieces supplied 

 with the instrument are nickel-plated. 



Leach's Improved Lantern Microscope. — The priucii^le upon which 

 this Microscope (figs. 101-103) is constructed, was briefly described in 

 a i^aper which Mr. W, Leach read before the Manchester Microscopical 

 Society in 1887, an abstract of which appeared in this Journal."" 

 There was no thought when this paper was read of placing the Micro- 

 scope in the market ; but the great amount of private corresj)ondence 

 which followed its publication, led to the instrument being manufactured 

 for sale. 



The stage used in it was an old and well-known form ; but it failed 

 to give satisfaction on account of the obstacles which the object-holder, 

 with its four arms and the springs coiled round, offered both to the 

 changing of the sub-condensers through the stage, and to the attachment 

 of a rotating tube for polarizing prism. To get rid of these obstacles a 

 new arrangement of object-holder has been devised and placed imder- 

 neath the stage, the arms passing through slots in the bottom, so as to 

 hold the objects against the inside surface of the front of the stage. 

 The new object-holder is thus placed out of the way of all the mechanism 

 and all the material used in the stage. In changing the sub-condensers, 

 all which it is now necessary to do is to take out the one in use and 

 substitute the other, neither object, objective, nor wheel of diaphragms 

 being disturbed in doing so. 



The compound wheel of diaphragms is peculiar in its construction. 

 One part of it has a large single aperture, and moves by means of an 

 arm upon a pivot, so that it can be lifted uj) out of the field or dropped 

 into it, just as it is or is not wanted. A spring catch holds it up in its 

 place, so that it cannot fall by its own weight. To the armed wheel is 

 attached a second wheel with five concentric apertures, any of which can 



See this Jourmil, 1887. p. 1019. 



8 K 2 



