RESINOGRAPHY 



light gets into the microscope and eye as a walls, floors and table-tops, so as to examine 



result of scattering by the object. Conse- them without destructive sampling. Special 



quently, paper, for example, appears white stands may be improvised, 



and a glass slide appears dark. Dark-field The biobjective (Greenough) microscope 



images by reflected light are the easiest to has inherent limitations of resolving power, 



interpret because they are of the same type The two objectives must be so close and at 



as received by the unaided eye. such an angle that their numerical aperture 



Transmitted illumination is typically is not much over 0.1. In fact, objectives of 



bright field in the Greenough microscope, all available magnifications have about this 



Paper, for example appears dark and a glass same numerical aperture, which is not much, 



slide appears bright. if any, greater than a hand lens. Therefore 



Reflected and/or transmitted light may the stereoscopic microscope cannot reveal 



be used with adequate control and inexpen- structure separated by much less than 5 ix 



sive lighting. With the simultaneously ro- (0.005 mm). The kinds and quantities of 



tatable polars and transmitted light, double properties are limited not only by the ob- 



refraction can be detected and studied during jective and focusing device but also by the 



heating or cooling under stretch or compres- illuminating systems. 



sion, or with other physical-chemical treat- Therefore, the resinographer's next micro- 



ments. scopical requirement would probably be a 



With its two objectives and an eyepiece high powered, polarizing light microscope. 



for each, the Greenough microscope is two Polarizing Light Microscope of High 



compound microscopes, one for each eye at Power. In resinography a light microscope of 



about the angle for maximum stereoscopic moderate power and quality of image is re- 



eft'ect. There should be little eyestrain or quired for the smaller sizes of Type IV units 



fatigue, provided that the prisms are in (Figure 12, right). The highest powers and 



adjustment. The Greenough microscope has qualities may be needed for Type III; they 



reinverting prisms so as to give erect images, certainly will be needed for Type II when- 



This feature is especially convenient in ever such small units can be made visible 



micromanipulation and experimentation: with light. In order to cover the whole 



Something pushed "north" and "east" does range of samples from transparent to 



not seem to go "south" and "west." Erect opaque, high powers must be available by 



images are interpreted as they would be either transmitted or reflected illumination 



with the eye unaided: If a texture is bright (2). That is, there must be both a substage 



on the side toward a lamp the texture is an condenser and a vertical illuminator and 



elevation, not a depression. each should be of high aperture, of good 



The two stereoscopic objectives have long image quality and with a polarizer. The 



working distances so that physical or chem- analyzer can be common to both illuminat- 



ical operations may be performed on the ors. A binocular eyepiece (so much used by 



object; for examples: scratch or impression biologists) is not used with polars and so is 



hardness testing ; tensile or compression test- not recommended for resinography.. The 



ing; electric, magnetic or electrophoretic combination (2) of "petrographic" and "ore" 



experiments; chemical reactions; etching or microscopes is recommended. The "petro- 



staining. graphic" part with its condenser and polar- 



The commercially available stands are izer for transmitted illumination is used 



versatile and interchangeable. The micro- for emulsions, suspensions, fibers, films, 



scope on the simple mount can be placed mounted grains and prepared thin sections 



directly on flat objects such as sheets, boards, (Figure 8, right). The "ore" part with 



533 



