ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



115 



The second is thus described (in English) by the designer : — " The 

 tube has three ouvertures o, o', and a ; a serves to place there a quartz 

 wedge ; o to place there a quartz plate, and o for the reception of a lens s, 

 which magnifies the axial image sketched by the objective, and which 

 conducts the rays of the objective, so that if we will pass from the ob- 

 servation in parallel light to that in convergent light, it is but necessary 

 to place the corresponding objective and the lens s without changing the 

 eye-piece, which can be exactly adjusted on the object by the aid of a 

 rackwork of the draw-tube h." 



The Microscope has the usual rotating stage, centering movements 

 to the body-tube h and h', diaphragm holder e, polarizer cZ, and eye-piece 

 analyser. 



Hughes' Patent Oxyhydrogen Microscope. — This instrument (fig. 6) 

 has been designed and constructed by Mr. W. C. Hughes " with a view 

 to enable scientists, teachers, and lanternists to display on the screen in 

 a clear and well-defined manner the minutiae of anatomical and geo- 

 logical sections, preparations of insects and vegetable tissues, and 

 general microscopic objects either by ordinary or polarized light. 



Fig. 6. 



" After a careful and protracted series of experiments, an arrangement 

 has been adopted by which the rays of light converging from a new form 

 of triplet condensers are concentrated into a narrow parallel beam which 

 will pass through the small apertures of the ordinary microscopic 

 objectives, and so be transmitted to the screen, without that loss which 

 is so disappointing in the ordinary lantern Microscope. 



" To obtain this maximum of illumination Mr. Hughes has designed 

 a special chamber jet, with which sufficient light can be obtained to 

 magnify transparent subjects to 1900 diameters, which has hitherto been 

 unattainable ; thus a flea, which is about 1/10 in. total length, will be 



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