THE MICROSCOPE. 13 



they bad been on board a sblp. Strict inj unctions 

 must be laid on all such not to approach the table 

 until the instrument is quite ready for them to take 

 a peep, coupled with a polite request that while 

 doing so they will keep their hands behind them. 

 A provision has been made which to some extent 

 provides for such an emergency. The object-glass 

 itself is screwed into a short tube, that fits accu- 

 rately the lower end of the compound body and 

 slides freely within it, being kept down in its place 

 by a spiral spring, which presses upon it from 

 behind. On the application of a slight force or 

 resistance to the object-glass the spring tube 

 immediately yields, within certain limits, to the 

 pressure, carrying with it the lens, which is thus 

 often saved from destruction. Object-glasses of 

 various degrees of magnifying power and excellence 

 of workmanship are supplied with the Microscope, 

 and may be purchased separately, according to the 

 wants and resources of the student. It will be 

 found that for all ordinary purposes the 1-inch and 

 ^-inch objectives are the most useful powers. A 

 substitute for the intermediate powers may be 

 obtained by pulling out the draw- tube and using 

 the higher eye-pieces. This method, though not so 

 satisfactory in its results as the use of separate 

 object-glasses, may be resorted to where a series 

 of objectives are not within the reach of the 

 observer. 



THE BINOCULAR MICROSCOPE. 



Since the invention of the Stereoscope attempts 

 have been made to apply the Binocular principle 

 in the construction of the Compound Micro- 

 scope. After some failures this desideratum has 

 been successfully achieved by Mr. F. H. Wenham, 

 a gentleman well known to microscopists by 



