44 CONSTRUCTION OF THE MICROSCOPE. 



the utility of the Simple, is the capability of being placed in either 

 a vertical or a horizontal position, or at any angle with the horizon^ 

 without deranging the adjustment of its parts to each other, and 

 without placing the eye-piece in such a position as to be incon- 

 venient to the observer. It is certainly a matter of surprise, that 

 Opticians, especially on the Continent, should have so long neglected 

 the very simple means which are at present commonly employed in 

 this country, of giving an inclined position to Microscopes ; since it 

 is now generally acknowledged that the vertical position is, of all 

 that can be adopted, the very tvorst, — excepting, of course, in 

 cases which necessitate its use. There are some objects which can 

 only be seen in a vertical microscope, as they require to be viewed 

 in a position nearly or entirely horizontal ; such are dissections in 

 water, urinary deposits, saline solutions undergoing crystallization, 

 &c. In ordinary cases an inclination of about 55° to the horizon will 

 usually be found most convenient for unconstrained observation ; 

 and the instrument should be so constructed as, when thus 

 inclined, to give to the Stage such an elevation above the table, 

 that when the hands are employed at it, the arms may rest con- 

 veniently upon the table. In this manner a degree of support is 

 attained, which gives such free play to the muscles of the hands, 

 that movements of the greatest nicety may be executed by them ; 

 and the fatigue of long-continued observation is greatly diminished. 

 Such minutiae may appear too trivial to deserve mention ; but no 

 practised Microscopist will be slow to acknowledge their value. 

 For other purposes, again, it is requisite that the Microscope should 

 be placed horizontally, as when the Camera Lucida is used for 

 drawing or measuring. It ought, therefore, to be made capable of 

 every such variety of position ; and the Stage must of course be 

 provided with some means of holding the object, when it is 

 itself placed in a position so inclined that the object would slip 

 down unless sustained. 



iv. The last principle on which we shall here dwell, is simplicity 

 in the construction and adjustment of every part. Many ingenious 

 mechanical devices have been invented and executed, for the pur- 

 pose of overcoming difficulties which are in themselves really trivial. 

 A moderate amount of dexterity in the use of the hands is suffi- 

 cient to render most of these superfluous ; and without such dex- 

 terity, no one, even with the most complete mechanical facilities, 

 will ever become a good microscopist. Among the conveniences of 

 simplicity, the practised Microscopist will not fail to recognize the 

 saving of time effected by being able quickly to set up and put 

 away his instrument. Where a number of parts are to be screwed 

 together before it can be brought into use, interesting objects (as 

 well as time) are not unfrequently lost ; and the same cause will 

 often occasion the instrument to be left exposed to the air and dust, 

 to its great detriment, because time is required to put it away ; so 

 that a slight advantage on the side of simplicity of arrangement 



