124 8CIOPTICON MANUAL. 



classes of lantern slides, because they are mostly after 

 the same designs. 



The set of long astronomical slides has from time 

 immemorial been accompanied by a printed lecture, 

 which, though somewhat antiquated, still answers a 

 pretty good purpose. 



Could a suitable lecture of similar shape accompany 

 each of the forty sets of scientific illustrations, it would 

 prove advantageous to many, and it would do no harm 

 to any; so we are looking for something of the sort in 

 the near future. But these sets of scientific slides them- 

 selves leave scarcely anything to be desired in the way 

 of fitness and excellence; and we have, moreover, in 

 the Sciopticon an instrument unrivaled for convenience 

 combined with efficiency. 



As before intimated, little has been attempted in this 

 chapter but to indicate some of the ways of finding 

 descriptions. 



When the use of the magic lantern was very limited, 

 its slides could be described in small compass ; but now, 

 a work that should describe all the slides in use, would 

 hardly be less voluminous than the Encvclopedia Bri- 

 tannica. 



