nachet's microscope. 



101 



hold one end of the slip of glass whereon is placed the object 

 under examination, whilst one of the other fingers of each 

 hand is used to push up the ^^^ 20. 



head at the end of the pin, 

 so as to lift the tongue from 

 the stage ; the slip of glass 

 can then be moved from side 

 to side, or up and down, 

 with the most perfect free- 

 dom, and may be firmly se- 

 cured at any point by ceasing 

 to press upon the heads of 

 the pins, which will then be 

 forced down by the springs, 

 so as to bring the tongues to 

 bea,r on the slip of glass. 

 When the microscope is used 

 in a vertical position, for the 

 examination of urinary de- 

 posits, &c., no means of fix- 

 ing the object being requir- 

 ed, it is convenient to turn 

 the tongues backwards, so 

 as not to occupy any part of 

 the stage. The advantages 

 of this arrangement are the 

 perfect fi-eedom with which 

 the slip of glass can be moved 

 under the objective, either in 



finding a minute object, or Nachet's compound Microscope. 



in examining the surface of a larger one ; and the facility 



and 



exactness with which it is retained at any point, at which it may 

 be desired to fix it. The disadvantages are, the necessity of 

 using both hands to move the object ; and the interference of the 

 tongues with the movement of the object from side to side, when 

 it is large enough to require a considerable range ; on which 

 last account the plan is unsuited to the use of an aquatic box. 

 The stage is furnished on its under surface with a diaphragm 

 plate, not mounted as a wheel, but sliding in a straight line, 

 which is a less convenient arrangement ; and to its lower side is 

 also attached a stem that carries the mirror, the distance of which 

 from the stage is not capable of variation. This instrument is 

 distinguished by its simplicity and cheapness, and by its adapta- 

 tion to many of the wants of the scientific inquirer.^ One of its 

 chief c?Madvantages is the small size (especially the narrowness) 

 of its stage, which cramps the operations of the observer ; and 

 hence it will not be found nearly so convenient to the young 

 microscopist, as the equally simple patterns in common use in 



' With three objectives and three eye-pieces, giving a range of magnifying powers 

 from about 50 to about 500 diameters, it is sold in Paris for 190 francs. 



