36 Modern Microscopy. 



better. In fact, some makers have constructed objectives 

 in very short mounts, working quite on to the prism up to 

 J- inch. These, however, are not recommended. Dr. 

 Carpenter some time since pointed out that when an 

 objective having more than 40 air angle was employed 

 with the Wenham binocular, spherical objects became dis- 

 torted, and instead of appearing round in shape they 

 became conical. The additional apparent advantage gained 

 is therefore useless. 



High -power prisms are also made by two or three 

 opticians, whereby higher powers may be employed with 

 a binocular microscope ; but we doubt whether the results 

 obtainable with them are really worth the additional outlay. 

 In those we have seen there has been such a very unequal 

 illumination in the two tubes, that, personally, we should 

 prefer using the instrument monocularly. Our advice on 

 this point would be : If you want to get the maximum 

 comfort in the employment of your microscope, have a 

 binocular, it will be found far more convenient and im- 

 pressive in showing to friends ; but if, on the other hand, 

 it is required for strictly scientific purposes, the monocular 

 will be found to do all that is required. Many microscopists 

 have separate monocular and binocular bodies fitted to their 

 microscopes, so that they may get the best results either 

 way. This is a very good plan. 



DISSECTING MICROSCOPES. 



These as a rule are of plain construction, sometimes 

 fitted with simple unachromatized lenses, but in the best 

 kinds with aplanatic lenses. The most important points 

 in this instrument are, that it should afford convenient rests 

 for the hands, should not be very high from the table, and 

 be provided with a glass stage. The desirability of always 

 using well-corrected lenses in this, as for all other purposes, 

 cannot be too strongly advised. The difference in cost in 



