168 MICROSCOPIC OBJECTS. 



(18.) A New Pocket Microscope. — "Portability is a 

 quality so essential in the opinion of many persons, that 

 I have been induced to construct a small instrument for 

 their use, which at the same time should be more con- 

 sistent in its principles than those in common use, and 

 I believe w^ill be found much more simple and equally 

 useful. Similar instruments before the public, to render 

 them portable, are separated into two or more pieces. This- 

 is obviated in my construction by the bar running within 

 a tubular stem. Another objection in the common ones 

 is, that in using high powers, the illumination is more 

 feeble than with low powers ; but it must be evident that 

 the reverse ought to be obtained, for the more we amphfy 

 an object the darker it becomes. In their construction 

 they remove the object farther from the light, the higher 

 the magnifying power ; in mine, the magnifier is brought 

 to the light, the object being stationary. The bar is tri- 

 angular, and therefore less liable to shake and loosen 

 than square ones. A rough sketch of the microscope 

 with the triangular bar partly drawn out to show the 

 rack, is here given, a are two magnifiers, of which 

 there are four ; they fit by a spring mto the arm at the 

 top of the bar ; these magnifiers are adjusted to the 

 object placed upon the stage b by the milled head c of 

 the pinion, and the light is directed through it by the 

 mirror d, which can be turned ^bout in any direction 

 and fits into the stand or block e. When the bar is 

 lowered and the magnifiers taken out of the arm, the 

 instrument, which is now only two metres and a quarter 



