. The Bell System technical journal . hotographing on film, or on plates. It is ;ised when a large numt)cr of small specimens are to be reproduced or when a large field is unnecessary. interesting exhibits as viewed in the beakers, but placed in suitablecells for ultra-microscopic examination, these licjuids come to life anddisplay the cf)lloidal particles coming into vision as tiny illuminatedparticles, only to burst into rings of light and pass away into the darkbackground. The constant irregular motion is the Brownian move-ment and the smaller the particle the more lively it moves. Conglom-
. The Bell System technical journal . hotographing on film, or on plates. It is ;ised when a large numt)cr of small specimens are to be reproduced or when a large field is unnecessary. interesting exhibits as viewed in the beakers, but placed in suitablecells for ultra-microscopic examination, these licjuids come to life anddisplay the cf)lloidal particles coming into vision as tiny illuminatedparticles, only to burst into rings of light and pass away into the darkbackground. The constant irregular motion is the Brownian move-ment and the smaller the particle the more lively it moves. Conglom- 120 BELL SYSTEM TECHNICAL JOURNAL crate masses of panicles merely float through the field of vision and,compared with the individual particles, appear exceedingly 20 gives a general view of the Zeiss ultra-microscope as originallydevised by Siedentopf and Zsigmondy. The equipment has beensuperseded to some extent by the later Siedentopf cardioid ultra-microscope. The latter is a very powerful light-concentrating device. I-ig. iO—The Slit ultra-microscoiic for transparent solid or liquid specimens. and U)v this reason it is |)riniarily .ulajjlcil for iIk exaniinatioii of finecolloidal solutions and dilute precipitates as well as for the observa-tion of micro-chemical and photo reactions. For transparent solidsand for the precursory examination of liquids and for rapidly passingin review several fluids in succession, the original arrangement retainsmarked advantages. The cardioid ultra-microscoi^e will be describedmore fully later on. Fig. 21 shows diagrammaticali>- the path of the rays within thepreparation in the presence of ultra-microscopic particles and willserve to make dearer what is to follow. In the original form of ultra-microscope (Fig. 20) the horizontal incident rays which go to furnishthe illumination do not enter the microscope, the latter being set upvertically and hence the background appears dark. The only raysto enter the objective of the vi
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
