New Prismatic Microscope Ocidar. By A. A. C. E. Merlin. 645 



eye-pieces is more likely to commend itself to the practical working 

 biologist. 



The prism, when used in conjunction with the x 12 long tube 

 ocular and a number of high and low power objectives on delicate 

 and sensitive objects, has been found to yield absolutely critical and 

 brilliant images, in every way as perfect as can be obtained without 

 it, while the eye-point is situated at a convenient distance from the 

 emergent surface, so that it converts an upright Microscope into a 

 most suitable instrument for prolonged observation in a comfortable 

 posture, and renders work pleasant which has hitherto proved most 

 trying and fatiguing, through the head being necessarily held down, 

 and the eye applied to the ocular in a constrained position, which 

 could hardly fail to injure such a sensitive organ ; thus, students 

 who have been heretofore forced by circumstances to do their work 

 in such discomfort are greatly indebted to Mr. Nelson for having 

 so ably compvited this little contrivance, which will entirely remove 

 their difficulties, without sacrificing the efficiency of the most 

 perfect apochromatic optical combinations, and will impart to a 

 non-inclinable laboratory instrument all the convenience of one 

 provided with a pivoted stand. 



It should, however, be noted that the new contrivance is not 

 suitable or intended for drawing, as the prism erects, but does not 

 transpose the object. For example, a letter F on the stage is seen 

 with the usual eye-piece inverted thus d, but with the prism added 

 it appears as -q. For visual observations, especially of small 

 living monads, bacteria, etc., this will be found of no practical dis- 

 advantage, and it is only of importance when a drawing is required, 

 for which purpose the prism should be removed. 



2 u 2 



