1882.] 



MICROSCOPICAL JOUKAL. 



47 



for their use we are indebted to the 

 courtesy of Prof. Kellicott. 



Fig. T4 represents Powell & Lea- 

 land's non-stereoscopic binocular 



LEFT LATERAL 

 PBI5M. 



for use with high powers, represented 

 in fig. 15. It is mounted the same as 

 the ordinary Wenham prism, and can 

 readily be substituted therefor. 



Fig. 16 represents the 

 Nachet stereoscopic binocu- 

 lar, and fig. 17 the Nachet 

 stereo-pseudoscopic arrange- 

 ment. It will be observed 

 that the two figures represent 

 the same instrument with one 

 of the prisms in different 

 positions, giving a stereo- 

 scopic effect in the first figure, 

 and a pseudoscopic effect in 

 the latter. 



RIGHT LATERAL 

 PRISM. 



Fig. 16. 



which may be used with high-power object- 

 ives. The prisms are mounted in a tube 

 which can be substituted for the tube hold- 

 ing the Wenham prism, now in common 

 use. The rays from the objective are 

 partly transmitted and partly reflected by 

 the surface of the prism B, and their 



Fig. 17. 



course can be followed by means of 

 the diagram. 



Mr. Wenham has devised a prism 



Fig. 18. 

 The ordinary Wenham bi- 

 nocular is represented in fig. 

 18. This is the form in al- 

 most universal use in this 

 country. 



Fig. 19 represents Prof. H. 

 L. Smith's arrangement by 

 which the rays from the ob- 

 jective are partly transmit- 

 ted and partly reflected by the plate 

 D. 



The first binocular of all was an 



