ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 



313 



movable through r to any height. By unscrewing n the arm can be 

 removed altogether. The magnifier I (a Briicke lens) is connected 

 with a by two shorter arms with ball-and-socket joints, Tc h. 



Fig. 63. 



B is the stand for the object. A hollow tube c, screwed into /, 

 holds a steel rod s, which can be removed up or down by the spring/; 

 a double arm hinged at g, and having a ball-and-socket joint h, carries 

 the forceps p for holding the object o. They can be moved up or 

 down in d. The apparatus has the great advantage of being movable 

 in any direction. 



In use, the apparatus is placed by the south window of the lecture 

 room, and, to obviate any unsteadiness, it stands upon a piece of felt 

 about an inch in thickness. A large sheet of white cardboard, for 

 which black can be substituted if necessary, is placed on the table as 

 a background for the object. To prevent too strong a light, there 

 are two frames — one having white calico, and the other black card- 

 board — which fit exactly into the lower part of the window. If the 

 light is required to fall on the object from above, then the black one 

 is used, but the white one if the light is to be dispersed. The speci- 

 men being arranged in a good light beforehand, one student after 

 another should examine it \ and the Professor has found that, after a 

 short description of the object, the student can dissect the specimen 

 more correctly, and can make a more accurate observation of its parts 

 at his desk than he would otherwise do. 



2. Use of the Sciopticon for Botanical Lectures. — Every teacher will 

 agree. Professor Hallier says, that there can hardly be too many 

 expedients for demonstrating objects in botanical lectures, the only 

 difficulty seems to lie in the choice of means. To illustrate the 

 teaching of natural science, the preference is always given to the 



