i$o OPTICAL PROJECTION 



better as a rule for this class of work than achromatics. Such 

 an object, for instance, as the head and tongue of a bee, can be 

 shown with the higher of the two powers very fairly, as regards 

 the general structure. 



There is great heat at the focus of the cone of rays, and 

 the microscopic attachment should therefore never be used for 

 more than a few seconds, without a large glass trough, filled 

 with saturated and filtered solution of alum, being first placed 

 in the ordinary slide-stage of the lantern. 



For exhibiting ordinary microscopic slides a wooden frame 

 is used, somewhat similar to the ordinary frames of lantern 

 slides. It is made to fit the stage of the attachment outside, and 

 the ordinary 3x1 inch micro-slides inside. This frame has 

 a movable end, by which the slides can be inserted in it as 

 required. 



With the double-stage instrument as shown in the figure, 

 more can be done. The two stages were meant to place slides 

 in position for the different powers ; but the second stage is 

 far better used in another way. In the centre of a wooden 

 slider made to fit the stage, mount a plano-convex lens as near 

 H-inch diameter as the slider will allow, and If to 2-inches 

 focus. Whenever the 1-inch or higher powers are in use, 

 place this lens, with convex side to the lantern, in the stage 

 nearest the condensers. Adjusting the lime by hand as before, 

 a great increase in light will now be gained, the cone of light 

 being brought down into a smaller space. It will be found 

 that decent results can now be obtained with higher powers, 

 even as high as or \ ir 3h, which will exhibit fairly such an 

 object as the tongue of a blow-fly. Ordinary microscopic 

 lenses may be used, with the help of a simple adapter. 



82. Improved Microscopic Attachment. This attachment 

 was first constructed by Messrs. Newton & Co., to produce the 

 foregoing results in a more handy way with ordinary achro- 

 matic microscopic objectives, and with something of the power 

 of the instrument hereafter described. It screws in the same 



