Microscopes and Accessory Apparatus Part 11

91. =Gla.s.s slide with cell= the floor of which is divided into squares, 1/400 square mm each, in box =4.--=

=Drawing Apparatus.=

The two following =drawing eye-pieces= Nos. 92 and 93, have quickly found favor among those having frequent occasion to make drawings from microscopic preparations and are now largely used in educational inst.i.tutions as an aid to students in the study of their specimens. In both eye-pieces the prism is so adjusted as to accomplish total reflection of the image, thus doing away with loss of light and with secondary reflections, such disturbing features of those forms of drawing apparatus of which a mirror forms an essential part.

[Ill.u.s.tration]

92. This =drawing eye-piece= is employed with the stand in the vertical position. The reflected image lies at the side of the microscope, the rays pa.s.sing off at an acute angle from the reflecting prism near the top of the eye-piece. The eye-piece slips into the tube of the microscope like any ordinary eye-piece and is held in position by a thumb-screw. The drawing field is at once visible without further adjustment, and the picture is clear and sharp. The brightness of the drawing field may be regulated by smoked gla.s.s plates mounted in two moveable metal arms =8.--=

[Ill.u.s.tration: Drawing eye-piece for drawing with inclined stand.]

93. This =drawing eye-piece= is similar in construction to that just described, but is so arranged as to throw the image vertically downwards behind the microscope when the latter is inclined at an angle of 45 degrees.

In this case also the picture reflected is clear and sharp, devoid of all disturbing secondary images. As the image is reflected vertically downwards upon the table, no special drawing stand is necessary as there is no distortion of the picture. The intensity of the light may be modified by smoked gla.s.s plates mounted in two moveable metal arms =10.--=

For a description of these drawing eye-pieces and of the principles involved in their construction reference may be had to the Zeitschrift fur wissenschaftliche Mikroskopie, XII, 1895.

[Ill.u.s.tration: Abbe's Drawing Apparatus.]

94. In =Abbe's Drawing Apparatus= the drawing field is reflected by a mirror at the side of the instrument and by a prism which fits over the eye-piece of the microscope. The prism is supported on a vertical hinge so that it may be readily turned out of the axis of the microscope without disconnecting the whole apparatus from the stand. It is shown turned to the side in the figure. A cylindrical cap accompanies the apparatus which fits over the prism holder and has six lateral windows in which are smoked gla.s.ses of various intensity, serving to regulate the lightness of the reflected drawing field =12.--=

[Ill.u.s.tration: Drawing Board No. 95. Drawing Board after Giesenhagen.]

The =Drawing boards= serve two purposes. They afford a smooth plane surface for the drawing paper and they are so arranged that they may be inclined at such an angle as to receive the rays of the reflected image at right angle to their surface, thus doing away with any distortion of the image on the paper.

95. This =drawing board= is especially adapted for use with drawing eye-piece No. 92. When in the position indicated in the figure its drawing surface forms an angle of 12 to the horizontal =2.--=

96. In =Giesenhagen's drawing board= the drawing surface may be adjusted at various angles and may be raised and lowered =4.--=

For drawing eye-piece No. 93 and the Abbe drawing apparatus the surface of the drawing board should be horizontal.

[Ill.u.s.tration: Drawing apparatus after v. Tubeuf.]

97. The =drawing apparatus= after v. Tubeuf serves for drawing objects from nature. By means of a prism mounted in a metal box, the object is reflected into the eye in such a manner that its image appears erected on the drawing surface. This is quite an advantage when drawing from nature but is unimportant when using a drawing apparatus on the microscope. Two smoked gla.s.ses mounted in moveable metal arms serve to moderate the intensity of the light. On the side of the prism nearest the eye is a small wheel diaphragm attached to regulate the size of the opening. The apparatus is mounted on a heavy nickel-plated stand with vertical and lateral adjustments controlled by thumb-screws =12.--=

=Mechanical Stages.=

[Ill.u.s.tration: Mechanical stage No. 98.]

98. =Mechanical stage= adapted to Stands I, Ia and Ib.

The stage is readily attached to the microscope by means of a small screw, _C_, which screws into a thread in the microscope just behind its stage, and binds the mechanical stage firmly in position and always in the same position. It may be again removed by simply uns.c.r.e.w.i.n.g this set screw.

The movements of the stage are at right angles to one another, are accomplished by carefully constructed rack and pinion adjustments and the exact position of each adjustment is indicated by vernier scales. The extent of the lateral movement is 50 mm; that of the other 30 mm.

This stage permits the careful and systematic examination of large specimens and its construction is so perfect that by means of the vernier scales the most minute objects may be readily replaced in the field of vision, even after removal and readjustment of the stage, provided only that their location when in the field of vision as indicated by the scales had been noted =28.--=

99. =Large mechanical stage= for stand, _A_, adapted for slides 50100 mm; both movements by rack and pinion adjustments =32.--=

[Ill.u.s.tration: Mechanical stage No. 100.]

100. =Mechanical Stage No. 100.= When a mechanical stage is ordered subsequently to a microscope outfit and under such circ.u.mstances that its correct adjustment to the stand by a skillful mechanic is impossible we advise the purchase of this more readily adjusted mechanical stage, which may readily be attached to Stands I, Ia, Ib, IIa and IIb by means of a thumb-screw. It is as carefully constructed as Mechanical Stage No. 98 and serves the same purpose in every particular =28.--=

100a. =New Mechanical stage=, simplified form =20.--=

[Ill.u.s.tration: Mechanical stage No. 100a.]

101. =Warm stage= after Schultze. This consists of a metal stage to which long lateral arms are attached, through which the heat from one or more small lamps is conducted to the central part of the stage and the object. The apparatus is also provided with a condenser, which affords illumination sufficient for the use of high power objectives, and with a thermometer indicating the exact temperature of the centre of the stage, which may be carried as high as 100 C. =12.--=

[Ill.u.s.tration: Schultze's Warm Stage No. 101.]

102. =Warm stage= after Pfeiffer. It consists of a gla.s.s chamber through which warm water may be made to flow. A small cell is ground in its surface thus permitting its use as a moist chamber =6.--=

103. =Warm stage= after Stricker. This stage consists of a metal chamber, through which warm water is made to flow when in use, and is provided also with a condenser and thermometer. It may be screwed firmly to any of the square microscope stages =14.--=

[Ill.u.s.tration: Stricker's Warm stage No. 103.]

104. =Warm stage= after Errera, permitting rapid changes from low to high temperature and vice-versa.

It includes 2 vessels for cold and hot water, mounted on tripods, with rubber-tubing etc. =24.--=

=Photo-micrographic Apparatus.=

[Ill.u.s.tration: Photo-micrographic Apparatus No. 105.]

The method of employing this apparatus and the general technique of photo-micrography are treated of in a separate pamphlet containing also four photo-micrographs taken with this apparatus.

This little work is furnished with each apparatus.

105. =The Photo-micrographic Apparatus= consists of a heavy iron foot supporting a stout column in which another iron support moves vertically. This latter holds the camera and may be firmly fixed at any height by means of a thumb-screw. This permits the accurate adjustment of the camera to microscope stands of various sizes. The length of the camera is also adjustable by means of a thumb-screw sliding in the upright support.

Regulation of the field of the camera is accomplished by a revolving disc diaphragm with openings of five different sizes situated in the neck of the camera. Two simple plate-holders for plates 912 and 1318 cm are supplied with each camera, as are also a ground gla.s.s plate and clear gla.s.s plate in the frame of the camera serve to catch the picture in the plane of the photographic plate, and a simple lens aids in obtaining a correct focus of the image. A white gla.s.s plate, mounted on a stand is of use in diffusing direct sunlight so as to make it available for photographic purposes, and three discs of yellow, blue and green gla.s.s are provided which may be inserted over the iris- diaphragm of the condenser when colored light is required.

It is of great advantage to interpose an illuminating lens between the source of light and the mirror, thereby condensing the light-rays, giving a uniform illumination and preventing the heating up of the entire stand, which is a disturbing factor in retaining the focus. The illuminating lens also serves to lessen the time of exposure.

This photo-micrographic apparatus is also available when it is desired to photograph gross specimens as, for example, embryos, insects, etc., by reflected light, as is represented in the figure on p. 86. The photographic objective of 64 mm focal distance, is best adapted to this purpose. It fits in a collar in the neck of the camera and yields a magnified image of about 3 diameters. The object is brought into proper focus by means of a small stand, the table of which may be raised or lowered as required.

Price of the apparatus without microscope stand =40.--=

106. =Small stand for supporting specimens= to be photographed by reflected light as mentioned above =4.75=

107. =Welsbach lamp= with reflector =6.--=