80O 



SUMMARY 01' CURRENT RESEARCHES RELATING TO 



and three objectives, over which are three prisms, which deflect the rays at 

 angles of about 45°. 



In order to make use of one mirror only, Mr. Ahrens fits beneath the 

 stage the arrangement of prisms shown in fig. 207, consisting of one equi- 



206. 



lateral and two rhomboidal prisms. These divide the rays from the 

 mirror, sending part into each of the side prisms whence they are reflected 

 into the two lateral objectives. 



A Microscope with several bodies and one objective so that the same 

 object may be viewed by several observers (as in the forms above described) 

 has obvious uses, while a Microscope with two bodies and hoo objectives is 



convenient for mounting purposes, as shown by Mr. Deby's Twin Micro- 

 scope.* Three bodies and three objectives (by which three observers can 

 look at three different objects at once) do not, however, afford the con- 

 venience of the former arrangement, while they make a useless addition to 

 the latter. 



The three objectives have a common focusing arrangement, no provision 

 teing made for focusing separately objectives of different powers. 



* See this Journal, 1886, p. 854. 



