BAUSCH Use and Care of the Microscope QH 205 B34 . \H SE AND CARE MICROSCOPE EDWARD BAUSCH EXTRACTS FROM MANIPULATION OF THE MICROSCOPE PUBLISHED BY PUBLICATION DEPARTMENT BAUSCH & LOMB OPTICAL COMPANY, ROCHESTER, N. Y. Copyright 4 LOME OPTICAL COMPANY, 1902. PKBSS OF I UK KAUSCH A LOMB OPTICAL CO., ROCHESTER. N. Y. USE AND CARE OF THE MICROSCOPE. Extracts from " Manipulation of the Microscope." How to Set Up the Instrument. Draw the instrument from the case by grasping the base and pillar ; free from dust with a large camel's hair brush, i inch or i 1-2 inch, or by wiping carefully with chamois skin, or old linen. Place the instrument on the work- table, which should be of such height that observations can be made with the utmost possible comfort without straining the neck, or compressing the chest. Bear in mind always to sit as upright as possible. If the instrument is used in the upright position, place the base close to the edge of the table ; if inclined, it may set farther in. Rest the arms, as much as the height of the instrument will permit, upon the table. Bring the tube to the standard length for which the objectives are corrected. To do this grasp the milled edge of the draw-tube and give it a spiral motion while holding the main tube with the other hand. There is one objection, however, that in any but cloth-lined sheaths the polished tube will soon be scratched, especially if not kept very clean. In stands without the graduated tube, a mark or ring is or should be Correct position at the microscope. provided on it, which should be co-incident with the upper end of the main tube. Where graduated tube is provided, bring the proper figure, either 216 or 160, in line with the upper end of the main tube in accordance with the tube length for which the objec- tives are corrected. Attach low power eyepiece. Attach low power objective. Place object on stage. Illuminate object. Focus on object. To Attach Eyepiece. The exterior surfaces of the eye-lens and field-lens, being exposed, are apt to become dusty, and should always be carefully cleaned before using. If there are two or more eyepieces, always use the lowest power first. Eyepieces should be so loosely fitted that they will drop into the tube as far as the collar by their own weight. They do this slowly when the objective is attached, as an air-tight compart- ment is formed and the air to the extent of the dimen- sions of the eyepiece must first be expelled from the tube. This displacement may, however, be hastened by gently pushing the eyepiece downward, but not to such an extent as to push in the draw-tube, or force down the coarse adjustment. In fact care must be used in applying the eyepiece, or sliding the draw-tube, as the focus may be disturbed, or the objective forced against the object and thus destroy it. To Attach Objective. Using a low-power objec- tive, remove from its box and see that its front lens is clean ; elevate the tube of the stand by means of the coarse adjustment so that the nose-piece shall be at least two inches from the stage. Proper manner of holding objective when attaching it to tube. Grasp the upper knurled edge of the objective between thumb and forefinger of the left hand ; bring the screw in contact with the screw of the nose-piece, and, keeping the objective in line with the tube and gently pressing upward, revolve the objective with the thumb and forefinger of the right hand by the lower milled edge until shoulder sets against shoulder. To properly attach an objective is not always simple, and cannot be done too carefully. One danger lies in the fact that the objective may be dropped onto the object, and thus injure or destroy one or the other or both, and another that the threads may be started wrong by holding the objective sideways, and the threads thus injured. To Attach Objectives and Double Nose- Piece. Screw each objective into proper place in the double nose-piece, with the 2-3 opposite the opening through which the light passes. Propei method of attaching nose-piece to microscope. Hold the nose-piece in the right hand, objectives down. Bring the revolving screw in contact with the screw in the tube, square with tube ; with thumb and forefinger of left hand, turn milled edge of the revolving screw until it engages, swing nose-piece toward the front, and, holding it in this position, screiv the ring home. The same procedure as above holds good for attach- ing objectives to the triple and quadruple nose-pieces. Finding an Object. The slide upon which the object is mounted is placed upon the front of the stage and slipped under the spring clips to a point where the object comes as nearly as possible in the center of the opening of the stage. With low power objectives, which are used on coarse and large objects, it will be found, after properly focus- ing, that a portion of the object will show itself in the field, and upon moving the slide it can easily be brought to the center. In this connection it must be remembered that the image in the eyepiece is in a reversed position from that of the object, and that a movement of the object to the left is an apparent movement to the right in the field. In case of a small object which is not found after the objective is known to be in focus, as may be told if the mounting medium or small particles of dust on the cover glass are visible, move the slide about -on the stage by grasping one end with the thumb and forefinger, when the object can usually be recognized by its shadowy out- lines as it flits across the field. The difficulty of finding an object or a particular spot in it becomes more difficult with the increase in power, and even in experienced hands sometimes becomes quite vexatious. Recourse may be had to two methods : By using a low power eyepiece. By using a low power objective as a finder. A large field is thus obtained in which the object may be more easily found, and after moving to the center of the field, the low power objective is removed and the high power attached ; or in case the revolving nose-piece is used, use the low power objective as a finder, then swing the high power objective into position, care being taken not to touch the slide, and focus in the manner to be described. The object may not be in the field, due to a slight variation in the centers of the objectives, but it will certainly be very close and ought to be easily found. To Illuminate the Object. This is an extremely important feature, and should always be carefully done, as one may easily fail to obtain the best results, may be led to wrong conclusions, or may injure the eyes. The mirrors of the microscope are usually plane and concave, and are provided^with universal joint so as to be able to reflect the light from any source in front or at the side of the microscope. The plane mirror reflects the light in the initial intensity of its source, and is used with low power objectives. The concave mirror concentrates the rays on the object, thereby giving intensified illumination, and is used with medium and high power objectives, except when substage condenser is used, when the plane mirror only is employed. The sources of light are either daylight or artificial light ; if the former the light of a northern sky is pre- Illuminating object with plane mirror. Illuminating object with concave mirror. ferred, and if the latter a flat-wick oil lamp or Welsbach gas burner. An ordinary gas flame should not be used on account of the difficulty of obtaining equal illumina- tion and the constant flickering which is very injurious. When using a flat-wick lamp the narrow edge of the flame should be used, as this is more intense than the broad side. When using daylight place the microscope, as nearly as possible, directly before a window, and when a lamp 8 is employed, have it on the table either in front or at the right side of the microscope and within easy reach. Light is either transmitted or reflected. When the former, it is used to illuminate transparent objects and passes through the objects from below the stage into the objective. With opaque objects this is impossible and reflected light is required, when it is directed onto the object from above and illuminates its upper surface. In the following instructions it is assumed that trans- mitted light is used unless otherwise stated. The concave mirror converges the light and its focus is of such length that with parallel rays (daylight) the light will fall on the object. With diverging rays (lamplight) the focus will be longer, and while ordinarily the mirror may remain in its position, it is advisable in critical work to properly focus the mirror by increasing its distance from the object. Before lighting an object make certain that the mirror bar is in exactly central position, and set the mirror at such an angle to the light that it will be reflected upon the object, which can be done more quickly at the outset by observing the object or the opening of the stage, keeping the head at one side of the tube. Now remove the eyepiece, and observe the light through the objective. It should be central and of equal intensity, which with daylight is sometimes difficult to obtain as the sash of the window may be reflected and show itself in the field as dark bands, or in the case of lamplight the blue portion of the flame may appear as a dark spot. These are only preliminary directions but will suffice for a beginning. There will be little difficulty in obtaining proper illumination at the outset if one will observe the following : Remove the eyepiece and, looking through the back of the objective, have Central illumination. Even illumination over the entire field. Mellow illumination. Defects in illumination which may not be apparent will show when the eyepiece is replaced, and are indicated, When dark points or shadows appear in the field. When the outlines of an object are bright on one side and dark on the other. When the object appears to lie in a glare of light. In the first two cases the correction can be made by suitably adjusting the position of the mirror, in the last by reducing the amount of light by the use of a diaphragm. It is now generally conceded that observations with the microscope may be made to any extent without any detrimental results to the eyes, provided, however, that the conditions of light are just right. It is a good rule to follow, to use as small an amount of illumination as will comfortably show the structure which is being studied, and it may also be safely accepted that, if the eye tires or feels uncomfortable, the light should be moderated. Illumination is either Central or axial, when the center of the mirror is in the optical axis, or Oblique, when the mirror is swung to one side, which in objectives of wide aperture will disclose struc- ture that cannot be seen with central illumination. To focus an objective is to adjust its relation to the object so that a clear image is obtained. Focusing should involve no danger to the front lens of the objec- tive, or to the cover glass by their coming in violent contact. With the low power objectives, in which the working distance is great, there should be little danger; with the higher power objectives, in which the working distance is so small that the front of the objective is very close to the cover glass, there is considerable. To focus low power objectives : Attach objective to the nosepiece. Lower the head to the level of the stage, watching the front of the objec- tive ; lower the tube by the coarse adjustment until the front of the objective is within one quarter inch of the object ; look through the eyepiece and slowly elevate by the coarse adjustment until the image is distinct. Use fine adjustment. The upward movement should be slow so that, if the object be faint, it is not missed and the adjustment not run beyond its focal distance ; or it is possible that, in the case of a very minute object, it may be out of the center, and thus out of the field of vision, in which case the surface of the cover glass, or the minute particles of dust upon it should be distinguishable. The object will first appear with faint outlines and indistinct ; then gradually more distinct, and finally sharply defined, and if adjustment goes beyond this point, it will gradually become more dim, in which case return to the point of greatest distinctness. To focus high power objectives : Attach objective to nose-piece. Lower the head to the level of the stage and look between objective and cover-glass toward a window or aflame. Slowly lower the objective with the coarse adjustment until the front of the objective is nearly in contact with the cover glass ; look into the eyepiece, slowly elevate the tube of the coarse adjustment until the image appears. Use fine adjustment. It is also advisable while watching for the image to appear to move the object slowly in different direc- tions, as the flitting of shadows or colors across the field will give indications that the objective is nearing the focal point. Always focus upward. In case a low power is exchanged for a higher power objective, or when the low power has been used as a searcher, i. e., to find a certain object in a collection, or a certain locality in a specimen, the tube should first be elevated, as working distance in the high power is too short to admit of screwing it into the nose-piece, then detach the low power, attach the high power and proceed to focus in the order given. Objectives which make up the regular outfits are so adjusted as to be par focal, i. e., are so fitted to the nose- piece that as either one is swung into position, it is so nearly focused as to require the use of the fine adjust- ment only. Very low power objectives vary so much in their focal lengths from those powers which make up the outfit that it is generally impossible to make them par focal. The 2-3 and 1-6 or 1-8 on the double nose- piece, and 2-3, 1-6 or 1-8 and the 1-12 oil immersion on the triple nose-piece are so made. But in a combina- tion of a lower power with 2-3 and 1-6 on the triple nose-piece, or a lower power with the 2-3, 1-6 and 1-12 on a quadruple nose-piece, it is impossible to get the lower power par focal with the others. As the adjustment of the objectives to make them par focal is quite delicate, each arm of the nose-piece is marked to correspond with the power of the objec- tive which is to go into it. Furthermore it is highly important to preserve proper tube length. In the short 13 tubes the objectives are adjusted for exactly i6o.omm. distance and if no revolving nose-piece is used, should be set for this length. With the revolving nose-piece the tube should be contracted so that the ring of the draw-tube rests upon the shoulder of the main tube. To focus with double nose-piece : Contract tube, focus with 2-3 objective, then swing nose-piece until 1-6 nears the cover glass, lower the head to the level of the stage and endeavor to slowly swing objective into place. Should the front of the objective threaten to come in contact with the cover glass, the tube must be elevated and the objective focused. The method of procedure with triple and quadruple nose-pieces is very much the same as with the double, and the same rules will apply. Oil Immersion Objectives. Immersion contact between the objective and cover glass is made \\ith cedar oil. This is specially prepared so as to have the same refractive index as glass and great care should be used to keep it free from dust. Apply the smallest quantity to the front lens, by allowing the superfluous amount to run from the rod or brush, before objective is attached to nose-piece. If air bubbles are contained in the oil, remove it and apply a fresh quantity. This is exceedingly important, as the presence of dust or air bubbles in oil may destroy the definition of the best objective. Attach the objective and loiver it until the fluid comes in contact with the cover ; observe this by lowering the head to the level of the stage. Focus as with dry objectives. Special care must be observed if a low power objective is used after an oil immersion. The oil must invariably be removed from the top of the cover glass by wiping first with a moist cloth, and then cleaning with a dry cloth. The front of the objective should always be cleaned in the same manner immediately after it has been used. To Focus with Fine Adjustment. After the focus has been found with the coarse adjustment, the fine adjustment should be brought into action, in order to obtain a more sensitive and reliable adjustment for focusing through the different planes or depths of the object. Its range of movement is necessarily short and at one end the screw comes to a stop, and at the other goes beyond the limit of movement and becomes inoperative. It should always be kept as near as possible at the medium point of its range. Grasp the milled head of the fine adjustment with the thumb and forefinger of one hand (right) and, turning the screw in either direction, focus in different planes of the object, while the other hand (left) moves the object. Use of Substage Diaphragm. The purpose of the diaphragm is to modify the amount of light, and by its aid obtain results in definition of the object which without it are impossible. Much will depend upon the density of the object, the intensity of illumina- tion and the power of the objective. Use an opening in Hie diaphragm of about the same size as the front lens of the objective. As a rule this will be found to give a superabundance of light, especially in low power objectives, and by reducing the aperture it will be found that there will be an increased differentiation in the object. The diaphragm should be reduced to a point where the amount of illumination will be perfectly comfortable to the eye. Do not use so large an opening that there will be an uncomfortable glare, nor so small that undue exertion is required to see structure. When oblique light is used, there should be no obstruction to the course of light, and with the iris and revolving diaphragms full opening should be employed. "Which Eye to Use. The right eye is generally used for observations, but, while the manipulator may from habit be inclined to use this, it may be possible that in some cases the left can be used to best advant- age and with less fatigue. 16 Make it a habit at the outset to keep both eyes open. There is a point over the lens called the eye-point at which the rays cross within the smallest compass, and this is the proper position for the eye. When above or below this point the size of field will be reduced or shadows or colors will appear in it. In low power eyepieces the eye-point is some distance from the lens, in high power quite close to it, in fact, in some, so close that the eyelashes rest upon the lens and sometimes appear in the field as dark bars. Cover Glass and Spherical Correction. The cover glass has a pronounced influence on the spherical correction of objectives. A variation in thickness from that used by the makers of objectives, while not appreciable in low powers, such as 2-3, may be very detrimental to satisfactory definition with a i -6 or a 1-8. Unfortunately, this effect is not generally known, or if so, not sufficiently appreciated. A variation of 0.05 mm. either thicker or thinner than the standard thick- ness'is sufficient tg totally obliterate the fine structure in an object, leaving the coarse fines only apparent, and a slighter variation affects the image proportionately. There is no one thickness adopted by the different makers and some even allow themselves considerable latitude in adjusting their objectives, so that there is a noticeably varying result with different objectives on the same specimen. Then, too, one great difficulty lies in the fact that it is commercially impossible to produce covers of one thickness. They are made in three numbers of the following thicknesses : No. i. 1-150 to 1-200 inch or 0.16 to 0.13 mm. No. 2. i-ioo to 1-150 inch or 0.25 to o. 16 mm. No. 3. 1-50 to i-ioo inch or 0.50 to 0.25 mm. The No. 2 cover glasses are in most general use, o.i 8 mm. thickness being best suited to objectives as now corrected. A good plan is to procure a cover glass gauge and measure the covers. Set aside those from 0.17 to o.ig mm. thick for use on specimens with which 1-6 or 1-8 inch objectives will be used. Those thicker may be laid aside for use with 2-3 and lower flowers , and the thinner ones for oil immersion objective. Under these conditions it is important to suggest methods by which the utmost efficiency of an objective may be obtained. To judge spherical correction by use of histo logical or biological objects and on Bacteria and Micrococc i with oil immersion objectives, without a previous know- ledge acquired from objects which are more suited, is extremely difficult, but a study in this direction will be found exceedingly valuable in utilizing the full capacity of the objectives. 18 To judge spherical correction with a 1-6 or 1-8, the diatom Pleurosigma angulatum is best suited to a preliminary study. Select a diatom which is flat and locate in the center of the field. Focus carefully so that the margin of the object will be sharply defined and observe the markings. If they should show in the same plane without any further focusing, the spherical correction may be accepted as being correct. If the lines appear to lie in a higher plane, and it is necessary to focus upward, so that the margin of the diatom is out of focus, it indicates spherical over- correction and the remedy is found in the contraction of the tube length. This should be done progressively in spaces 01^ about one-half inch, and after each change carefully focus again until proper correction is obtained. When the lines appear to lie below the plane of the object, it indicates spherical under-correction, and can be corrected by increasing the tube length. If there are two or more eyepieces, results can be obtained quicker with the higher powers. If the mark- ings cannot be seen it may be due to abnormally thick or thin covers, a not uncommon occurrence, thus destroying the resolving power. This may be judged by using slightly oblique illumination. If too much is used the nice differences will be lost. If from a pre- conceived idea of what any other object should show it is hazy where one expects it to be distinct, or if it fails to show detail which is known to exist, and being certain that the objective and eyepiece are properly cleaned, it may generally be ascribed to lack of proper correction. By focusing either above or below the proper focal plane, there will be an enlargement of the outlines of the object or a coma, which gradually enlarges as the objective recedes from the proper focal point. If the expansion or coma is greatest when the objec- tive is elevated, there is spherical over-correction, and the tube length should be decreased. Should the expansion be greatest when the objective is lowered, there is spherical under-correction and the tube length should be increased. ILLUMINATION WITH SUBSTAGE CONDENSER. Purpose of the Condenser. The purpose of the condenser is to give an amply illuminated field when the illumination is otherwise insufficient, and to illuminate the object with a cone of light having an angular aperture equal to that of the objective, as well as to provide means for controlling the amount and character of the illumination to suit the various condi- tions of work. Abbe Condenser 1.20 N. A. Abbe Condenser 1.42 N. A. The Abbe condenser of 1.20 N. A. is in most common use and the most simple form of mounting is one which has attached to its lower side an iris diaphragm for regulating the amount and angle of light and a vertical screw motion. The most complete form has adjustments for obtaining every modification of illumination, with rack and pinion for vertical and lateral adjustment. 21 The condenser should not be used on very low power objectives as it is distinctly harmful and the mirror alone provides ample illumination. Use only plane mirror with the condenser. A condenser is so constructed that parallel rays of light are brought to a focus above the upper surface of its uppermost lens and in the plane of the object, If the concave mirror is used the convergence of light is more rapid and the apex of the cone of light is \vithin the condenser and its effectiveness depreciated. Illuminating object with condenser and plane mirror. The right way. Illuminating object with condenser and concave mirror. The wrong way. Centering the Condenser is the act of bringing its optical axis coincident with the optical axis of objective. To verify correct centering two easy methods may be followed : /. Use a 2-inch objective and focus through the condenser onto the diaphragm, which is reditced to its smallest opening. //. Use a 2-3 or i inch objective ; focus upon upper surface of condenser or upon an object which should then be removed ; elevate objective with coarse adjust- ment until a dimly defined dark spot appears in the field and with proper focusing is about i-j of the diameter of the field. Centering of the con- denser does not imply that the cone of illumination is also centered and it is fully as important to secure the correct conditions in one as it is in the other. Complete Substage. Front View. Centering the Illumination. The mirror may be so adjusted that the light will be directed toward the periphery of the condenser and when lamplight is used the light may be so placed as to give all grada- tions of oblique illumination from the central to the limit of aperture, although the condenser may be centered. With daylight have evenly illuminated field. With lamplight attach 2-3 inch objective ; open dia- phragm to full extent and focus upon the minute image of flame ; adjust mirror so that the image will be in the center of the field. 2 3 To Focus Condenser. In all the various forms of mountings the condenser is so mounted that at the uppermost limit of adjustment its upper surface is just below the surface of the stage so that it cannot come in contact with the slide. With all objectives having a numerical aperture less than i.o the condenser may be used dry, i. e., without oil. Complete Substage. Front view, with condenser and lower iris diaphragm swung out of optical axis. In the use of the condenser with oil immersion objectives the custom prevails of using the condenser dry. It is well to point out, however, that both the condenser and the objective lose in their efficiency when the former is used dry, and for critical work the condenser should be in immersion contact with the slide. To make immersion contact between condenser and slide place a drop of oil on the top of condenser, drop the slide upon the stage, first throwing the clips to one side. With immersion objectives the proper focusing of the condenser becomes a matter of nice distinction to obtain best results and can only be reliably accomplished by considerable practice and experience. To obtain best position : Use a 2-j objective ; focus upon the object ; adjust condenser until image of window-sash or flame is in the same plane with the object. Complete Substage. Top view, with condenser and lower iris diaphragm swung out of optical axis. Relation of Aperture of Condenser to Objective. In the study of Bacteria and other micro- organisms, the objectives used being of wide aperture, it is sought to have them stand out boldly in a bright field. This is accomplished by bringing the diaphragm to its full aperture. On all other objects, however, too much illumination decidedly injures definition by obliterating detail. Little experience is required to judge when the con- denser has its proper opening. When correct, the image will stand out sharply defined without any appearance of fogginess and as the diaphragm aperture is reduced it will be noticeable by the decrease in the amount of light. By removing the eyepiece and looking at the back of the objective the relative aperture of the con- denser to that of the objective may be easily seen, as the outlines of the diaphragm are sharply defined. In testing for this start with the smallest aperture of the diaphragm and gradually increase its diameter. If the opening in the diaphragm appears to have the same open- ing as the back of the objective, the condenser has the same angular aperture. In the following instructions for the proper use of light from the condenser the size of opening of its diaphragm as it appears by viewing the back of the objective is called apparent aperture. By experience the following conditions have been found to give most satisfactory results : In oil immersion objectives on bacteria use the full opening of diaphragm. On diatoms reduce the apparent aperture to about two-thirds opening in objective. In histological and other dense objects use the apparent aperture equal to about one-half the opening of back lens in objective. In dry objectives the aperture of the condenser should always be less than that of the objective. 26 Oblique Light with Condenser. Oblique light may be obtained by setting the mirror alone in such a position that the light reflected from it shall enter the condenser only at one side, leaving the balance of it unused. This, however, is only advisable when the condenser mounting has no other provision for obtaining oblique light. In the mountings having such provision oblique illumination may be obtained by two methods': /. Focus objective ; re- duce the apparent aperture to that of the rear lens of the objective, swing the plate o, page 23, carrying the lateral adjustment around so that the pinion button is at the front. Turn the pinion button so that the opening will move from the center to the periphery of the condenser. II. Proceed as above with this difference. Remove eyepiece and view the bright circle of light as it passes from the center to the periphery of the rear lens. When the circle of light has passed beyond the limit of aperture of the objective the field will become dark. In objects with striated structure, the illuminating rays should be brought to a position at right angles to Illuminating object by oblique light with condenser. the striae, either by rotating the object to the proper position, or by swinging the diaphragm plate. In using process II the circle of light should be bright. As it nears the edge, colors become apparent until finally at the edge of the objective the violet and red are quite pronounced. With proper disposition of the mirror the colors may be so equalized that after a little practice the illumination will be found at its best after the eyepiece is applied. With either method lamplight will be found to give best results, but care must be taken that, as the dia- phragm passes toward the oblique point, the mirror is also adjusted so that the illumination will not be lost. In the Abbe condenser the chromatic aberration is quite apparent with extreme oblique illumination. The field ceases to be equally illuminated and all the colors of the spectrum from the violet to the red are plainly evident within the field of view. Under these condi- tions it is of course impossible to view large specimens without slightly shifting the mirror so as to move the lightest portions of the spectrum to different parts of the field. With small specimens the mirror should be so directed that the light or yellow portion of the spectrum is in the middle of the field. CARE OF A MICROSCOPE. Besides acquiring the ability to properly use an instrument with its accessories, it is important to know how to keep it in the best working condition. It may be said without reserve that an instrument properly made at the outset and judiciously used should hardly show any signs of wear either in appearance or in its working parts, even after the most protracted use ; and further than this, every good instrument should have a provision for taking up lost motion, if there is a likeli- hood that this may occur in any of the parts. Especial care should be given to the optical parts, in fact such care that they will remain in as good con- dition as when first received, after any amount of use. Accidental injury may occur, but is quite unlikely if a systematic manner of working is followed, if a special receptacle for each part is provided. Do not allow any person except your teacher to manipulate your microscope or accessories. One person may be expert in the manipulation of one instrument and still find it difficult to work with another. The fine adjustment particularly causes the 29 greatest difficulty, as in some instruments the move- ment of the fine adjustment is in a direction opposite to that of the micrometer screw, and thus the objective as well as the object is endangered. If the microscope is to be carried any distance it should be done in its case. Avoid exposure of the microscope to direct sunlight and extreme or sudden changes in temperature. If by chance the microscope should have become very cold, as during transportation in winter, allow it to warm gradually. Care of the Stand. Keep free from dust is one of the first rules to be observed. When not in use place the microscope in its case or cover with a bell jar or close mesh cloth such as cotton flannel or velvet which should reach to the table. If the case will not receive the entire outfit, remove the double or triple nose-piece, it these form part of it, and place objectives in their cases If dust settles on any part of the instrument remove it first with a camel's hair brush and then wipe carefully with a chamois skin, wiping with the grain of the finish of the metal and not across it, as in the latter case it is likely to cause scratches. When handling the stand, grasp it by the pillar or stage. While the arm is the most convenient part it is at the same time the most dangerous to the fine adjustment. 3 Avoid sudden jars, such as placing upon the table or into the case with force. Remove any Canada balsam or cedar oil which may adhere to any part of the stand with a cloth moistened with benzole and wipe dry with chamois. Use no alcohol on any part of the instrument as it will remove the lacquer. As the latter is for the purpose of preventing oxydization of the metals, it is important to observe this rule. To use the draw-tube impart the spiral motion. To lubricate any of the parts, use a slight quantity of soft tallow or good clock oil, or paraffine oil. If the pinion works loose from the jar incident to transportation or long use, which sometimes occurs to such an extent that the body will not remain in position, increase its tension by tightening the screws on pinion cover. Occasionally withdraw the tube from the arm, wipe clean and lubricate both slides. This is highly important as the slides being constantly exposed become dusty and the lubricant is inclined to gum. Apply a small quantity of soft tallow or good clock or paraffine oil to a cloth, wipe well over the surfaces and remove the superfluous amount with a dry cloth or Japanese paper. If the lubricant becomes gummy, remove by wiping with a small quantity of benzine or benzole applied to cambric. Do not apply oil or grease to the rack or pinion as this will act as a dirt catcher and wear out the teeth at the points of contact. In inclining the stand always grasp it by the arm and never by the tube, as in the latter case it may loosen the slide or tear off some of the parts. In using a screw driver grind its two large surfaces so that they are. parallel and not wedge-shaped, so it will exactly fit in the slot of the screw-head. Turn the screw with a slow steady motion pressing the screw- driver firmly into the slot. No screw-head will ever be injured if these points are observed. When repairs or alterations are necessary, always have these made by the manufacturers who can, from a system of duplicated parts, do it not only cheapest, but best. Joint for Inclination. If the joint should become loose so as to prevent the arm being set at any angle of inclination, it should be tightened by drawing up the nut at one or the other side. If the nut has screw slot use a properly prepared screw driver, but if two holes a suitable key should be obtained from the maker. In high grade instruments the axle is generally tapering, and to determine which nut is to be drawn up can only be done by trial. Care of the Coarse Adjustment. Special care should be given to keep the coarse adjustment free from dust as its effect is particularly pernicious. The slides and rack and pinion are necessarily exposed and the lubricant is apt to catch dust and also to gum. The tube should be occasionally withdrawn from the arm and the slides carefully wiped with a cloth moistened with benzole. Lubricate by applying a small quantity of soft tallow or paraffine oil to a cloth and wiping well over the surfaces, removing the super- fluous amount with a dry cloth. The teeth of neither rack nor pinion should ever be lubricated. An occasional cleaning of the teeth with an old tooth brush is advisable. It is advisable occasionally to lubricate the pinion shank on both sides of the arm with a very minute quantity of paraffine oil. If the pinion works loose from jar incident to trans- portation or long use, which sometimes occurs to such an extent that the body will not remain in position, increase the friction upon it by tightening the screws on the pinion cover. Fine Adjustment. In a general way it may be said that if the fine adjustment ceases to work satis- factorily the instrument had better be returned to the maker, as it involves the most delicate working and few people are conversant with its construction. There 33 is very seldom any occasion for this, however, if used with reasonable care. If the fine adjustment does not respond to the turning of the micrometer screw, or if it comes to a stop, it indicates that the adjustment screw has come to the limit of its motion at either end. It should by no means be forced ; it should at all times be kept at a medium point. The micrometer screw should never be removed unless after long use it works with a pronounced gritty feeling. In this case unscrew from its bearing, wipe clean with a cloth moistened with benzole, and after wiping dry apply good tallow, being careful to start the threads properly. If they are not properly started much mischief may be done. In some instruments the threads are left handed. In removing the screw observe whether there is a small steel pin in a recess in it, and if so be careful that this is in proper position when returned or else the fine adjustment will be inoperative. Screw-Driver. Ordinary screw-drivers are not fit for use on the microscope. A properly made screw- driver should be ground on its two large surfaces so that they are parallel and not wedge shaped, so that it will exactly fit in the slot of the screw head. In using, turn the screw with a slow, steady motion, pressing the screw-driver slowly into the slot. No screw head will ever be injured or marred if these points are observed. 34 Care of Objectives and Eyepieces. Every outfit should be provided with a camel's hair brush and a well washed piece of linen. On account of its fine texture chamois skin is desirable, but only after it has been repeatedly washed. No dust should be per- mitted to settle upon nor should the fingers come in contact with any of the surfaces. Occasional cleaning is desirable even when they ( ' o and e p ) are not used, as a film settles upon the outer as well as the inner surfaces of the eyepiece and the rear surface of the objective, and creates a cloudiness in the image. When not in use objectives and eyepieces should be kept in their receptacles. If objectives are left attached to the microscope either singly or on revolv- ing nose-pieces, leave the eyepiece in the tube so that no dust can enter and settle upon the rear lens of the objective. Objectives especially should be kept where they are not subject to extreme and sudden changes of temperature as the expansion and contraction may cause the cement between the lenses to crack. Also avoid direct sunlight, as the cement may soften sufficiently to ooze out. Eyepiece. Visible defects in the field are always traceable to impurities in the eyepiece, not in the objective, and are easily recognized by revolving it. Indistinctness in the image or loss of light may be due 35 to soiled or coated surfaces in either eyepiece or objective. Dust if on either the eye-lens or field-lens is apparent as dark, indistinct spots. To clean the surfaces, breath upon them and, giving a revolving motion to the eyepiece, wipe with well washed linen and finally blow upon the surface, or use camel's hair brush to remove particles of lint. At regular periods unscrew the eye-lens and field lens and clean the inner surfaces. Objective. This should be used with the utmost care. The systems should never be separated, even if they can be unscrewed, as they are liable to become decentered and dust may enter. Avoid all violent contact of the front lens with the cover glass. The oil immersion objectives are partic- ularly sensitive and easily ruined. Screw into the nose-piece and unscrew by grasping the knurled edge and keeping in line with the tube. Occasionally examine the rear surface of the objec- tive with magnifier and if dust be present remove with camel's hair brush. Clean an immersion objective immediately after it has been used by removing the fluid with moist cloth and wiping clean with dry cloth or lens paper. While cleaning give the objective a revolving motion. 36 If the immersion oil should hare become thick, or any substance adheres to the surface, which cannot be removed by wiping, apply a small amount of benzine to a cloth and wipe carefully but quickly, so that the fluid will not affect the setting of the lens. Wipe clean with dry cloth. Do not apply alcohol to objectives under any con- dition. If any part of the microscope cannot be brought to a satisfactory working condition by the foregoing instructions, or any part is injured by accident it should invariably be sent to the maker or to a well known manufacturer of microscopes. INDEX. Abbe Condenser Aperture of Condenser 25 Apparent Aperture 26 Care of Microscope 29, 37 Cedar Oil 14, 31 Centering Condenser 22 Centeringlllumination 23 Coarse Adjustment 33 Complete Substage 23 Concave Mirror 8, 22 Condenser 21 Aperture of 25 Oblique Light with 27 To Center 22 To Focus 24 Cover Glass 17 Diaphragm How to Use Draw Tube 16 26 1, 3 Eye, Which to Use 16 Eyepiece, To Attach 3 Care of 35 Eyepoint 17 Finding an Object 6 Fine Adjustment 15, 33 Focusing Condenser 24 Focusing Objectives 11,15 Immersion Objectives 14 Immersion Oil 14, 37 Illuminating Object 7, 21 Illumination, To Center 23 Joint for Inclination 32 Micrometer Screw 34 Microscope, Care of 29, 37 Correct Position at 2 To Set Up 1 Mirrors 7, 8 Nose-Piece, To Attach 5 To Focus with 14 Object, To Find 6, 12 To Illuminate 7, 22, 27 Objective, To Attach 4,5 Aperture of 26 Care of 35, 36 Cover Glass with 18 Oil Immersion 14 To Focus 11 To Test 19 Oblique Light 27 OilImmersionObjectivel4 Over-Correction 19 Par Focal Objectives 13 Pinion 31 Plane Mirror 7, 22 Screw Driver 32, 34 Searcher Objective 13 Spherical Correction 17 To Test for 19 Stand, Care of 30 Substage, Complete 23 Substage Condenser 21 Substage Diaphragm 16 Tube Length 1, 13, 19, 20 Under-Correction 19 MANUFACTURES of the BAUSCH & LOMB OPTICAL CO. MICROSCOPES Objectives, Micrometers, Camera Lucidas, Magnifiers, Dissecting Microscopes, Stains, Mounting and Imbedding Substances, etc. MICROTOMES Minot Automatic Rotary, Minot Automatic Precision, Laboratory, Student, Demonstration, Hand, Freezing. Fine Dissecting Instruments, etc. PHOTOGRAPHIC APPARATUS Bausch & Lomb-Zeiss Anastigmats, Telephoto Lenses, Shutters, Complete Photomicrographic Cameras, Projection Apparatus, etc. PRISM FIELD GLASSES Bausch & Lomb-Zeiss Stereo and Bausch & Lomb Prism Binoculars. BACTERIOLOGICAL APPARATUS Incubators, Sterilizers, Autoclavs, Centrifuges, Blood and Urinary Apparatus, Nutrient Substances, etc. CHEMICAL APPARATUS & CHEMICALS Fine Balances, Pure Platinum Ware, Glassware of every description, Analytical Chemicals, etc. BAUSCH & LOMB OPTICAL CO. ROCHESTER, N. Y. NEW YORK CITY CHICAGO CATALOGUES AND BOOKLETS issued by the BAUSCH & LOMB OPT. CO. A Microscopes and Accessories B Microtomes and Apparatus for Microtomy C Photomicrographic Apparatus D Projection Lanterns, Accessories, and Lantern Slides B Bacteriological Apparatus F Chemical Apparatus O Chemicals and Reagents H Photographic Lenses, Shutters, and Accessories Bausch & Lomb-Zeiss Stereo Binocular Field Glasses Bausch & Lomb Prism Binocular Field Glasses Centrifugal Blood and Urine Analysis Bausch & Lomb Plastigmat Lens Bausch & Lomb Shutters Any of above sent free on request JOURNAL OF APPLIED MICROSCOPY AND LABORATORY METHODS A monthly record of practical methods and apparatus from the best laboratories of the world. Review departments of Botany, Cytology and Embryology, Zoology, Physiology, Histology, and Bacteriology cover the latest literature of every language. A department of Laboratory Photography is devoted to the advancement of methods and apparatus for photographing both macroscopic and microscopic objects. The Journal is supported by the highest authorities in America and is a reliable reference book for science teachers, physicians and all who are interested in the microscope. Price per Year f i.oo in Advance 001 267760 5 THE LIBRARY UNIVERSITY OF CALIFORNIA Santa Barbara THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW.