warington's microscope-stand. 447 



this useful and ingenious microscope, referred to at page 51 of our 

 book. Fig. 216 is a representation of it as it appears when put 

 together ready for use ; and fig. 217 shows it taken to pieces, and ready 

 for packing in a leather case. The simplicity of arrangement here 

 exhibited must commend itself to every microscopist. It is unneces- 

 sary to give a lengthy description of it : and we content ourselves by 

 observing, that it is firmly clamped to the stand or wood bottom, and 

 l)y means of this same clamp it can be fixed to the side of a vivarium 

 or table. The draw-tube itself is the coarse adjustment, whilst a finer 

 is secured by a well-made union-joint, into which the object-glass is 

 screwed. With an additional arm for the reception of a single lens, 

 it can be converted into a dissecting microscope. It is a cheap 

 and useful form of instrument, either for the student or sea-side 

 purposes. 



fig. 217. 



Other makers have turned their attention to the manufacture of 

 cheap instruments to meet the requirements of students; among whom 

 we may mention Messrs. Smith and Beck, and Messrs. Field and Son 

 of Birmingham. 



M. Dujardin found that, to produce the best efiiects, a prism of 

 glass should be used instead of a mirror. The prism should be so 

 arranged as to slide upon the end of the condenser, and turn upon it 

 in such a manner, that in whatever position the lamp or light may be, 

 the prism may be adjusted to it. The quantity of light passing through 

 it is greater than with the mirror ; and those test objects in which deli- 

 cate markings exist, are seen to much greater advantage in consequence 

 of all the rays being reflected from the same surface, which is not so 

 with a silvered glass mirror. 



Mr. John Furze has lately directed the attention of microscopists 

 to a beautiful arrangement for the " illumination of objects by polarised 

 light on a dark field, in such a manner as to give the object a stereo- 

 scopic effect by a due contrast of light and shade." To obtain this re- 

 sult, he uses a plano-convex lens, three-fourths of an inch in diameter. 

 This, when fitted, is of so small a size, that it can be adapted to any 



