PROJECTIONS. 43 



through the objective above it, and falls upon a 

 second mirror, which is so mounted as to allow 

 reflection in any direction. The same device is 

 made a part of the " College Lantern," manufactured 

 by Hawkridge, of Hoboken, N. J. By an ingenious 

 arrangement the change from the horizontal to 

 the vertical can be made in less than half a minute. 

 The microscope, the polariscope, the electric-light 

 regulator, and several other fixtures, are fitted to 

 this instrument, making it a most perfect and complete 

 lantern. 



Such a vertical attachment as is shown in Fig. 25 is 

 applicable to the porte lumiere, but one can be extem- 

 porized, that will do good service, with such material as 

 is accessible to every one. An iron filter-stand, such 



Fig. 27. 



as is in common use in every chemical laboratory, may 

 be taken, and the condensing lens c laid upon the lower 

 or largest ring, and the objective, <?, upon the upper or 

 smaller one, as shown in Fig. 27. Below the lower ring, 

 a plain mirror m may be placed, at such an inclination 

 that the beam of parallel rays falling upon it from the 



