772 SEC. 18. BIOLOGY. 



This instrument, of which the general construction is that of Ross's English 

 microscopes, is remarkable for the following arrangements : It may be used 

 in three different positions, vertical, horizontal, or oblique, and is specially 

 applicable to the photography of microscopic objects. The illumination 

 is effected by means of a mirror carried by a system of jointed rods, which 

 limits its movement to an arc, the centre of which is the object to be observed. 

 The best illumination is thus quickly procured, the observer not having to 

 regulate at the same time the focal distance of the mirror and its lateral 

 distance from the axis of the microscope. The condenser is moved by the 

 help of a crank, which serves to regulate exactly the position of the diaphragm. 

 The whole condensing system, turning around an eccentric axis, can be very 

 rapidly modified. 



The stage turns independently of the tube. The focussing is effected, for 

 coarse adjustment, by means of a crank, and for fine adjustment by means of 

 a milled screw acting upon the tube supporting the objective, by the inter- 

 vention of a lever that lessens the amplitude of the movement. 



The tube supporting the objective is carried by a spring which serves to 

 prevent the objects being crushed, when by mishap the objective is lowered 

 too quickly. The milled screw for focussing is used as well for the micro- 

 metrical measurement of objects under observation, as for regulating the 

 chemical force in the use of the objective in photography. 



The objective is not screwed on to the tube, it is only pressed by spring 

 pincers against a steel bearing adjusted with the greatest care. To take off 

 the objective, it is sufficient to draw it away transversely by pressing in the 

 direction of the tube of the microscope. The objective is fixed as instan- 

 taneously as it is removed. The advantages resulting from these arrange- 

 ments are the following : 1st. A great saving of time to the observer. 2nd. A 

 mechanical centring of the whole objective much more perfect than that 

 obtained by a screw. The defects of centring being immediately discovered 

 may be partly corrected. 3rd. There is the easy choice of the side of the 

 objective that gives the best effect when the oblique illumination is employed. 



3582. Microscope, with durable body, with rotating move- 

 ment round its axis, fine adjustment by means of steel prism, 

 condenser, polarizing apparatus, magnifies from 10 to 1,200 dia- 

 meters. W. Teschner (successor to Amuel), Berlin. 



3583. Microscope, with magnifying power from 20 to 1,000. 



W. Teschncr, Berlin. 



3586. Polarizing Microscope, for showing rings in double- 

 refracting crystals. Dr. Stone. 



3587. Polarizing Microscope, with movable body and 

 prism. M. A. Picort, Paris. 



3588. Polarizing Microscope, with movable body. 



M. A. Picort, Paris. 



3589. Picort Vertical Polarizing Microscope. 



M. A. Picort, Paris. 



3589a. Polarizing Microscope, with lens for parallel light, 

 and Nicol prisms for measuring the axes. Laurent, Paris. 



