348 



SCIENTIFIC AMUSEMENTS. 



Eye-piece. 



Body. 



Body tube. 



and to prevent scattered light from surrounding objects from 

 reaching the eye and so rendering it less sensitive to the impres- 

 sion produced by the rays passing through the instrument ; they 



do not directly con- 

 tribute to the forma- 

 tion of the image. 

 A home-made astro- 

 nomical telescope, 

 with an eyepiece 

 consisting of a 

 double convex lens 

 of about 1 inch focal 

 length and half or 

 f inch diameter, 

 together with an 

 object-glass of 1J or 

 2 inches diameter 

 and 30 inches focal 

 length, will magnify 

 some 30 or 40 di- 

 ameters ; a power 

 sufficient to enable 

 Jupiter's moons and 

 other interesting 

 celestial objects to 

 be distinctly seen on 

 a clear night, especi- 

 ally if the telescope 

 is mounted on some 

 kind of a stand to 

 steady it, instead of 

 holding it in the 

 hands. 



Expt. 376. The 

 Compound Micro- 

 scope. The astro- 

 nomical telescope, as 

 above stated (Expt. 

 374), is in principle 

 a camera obseMra 

 combined with a 

 simple magnifier ; in 

 the same kind of 



Stage. 



Fig. 192. Microscope showing the different parts 

 of the Instrument/ 



way a compound microscope is substantially a magic lantern com- 



