. The microscope and its revelations. that when thecondenser is racked the exteriorshape of the illuminatedportion will becomemore circular, two darkpatches will appear oneither side of the centre,showing the operationof the spherical aber-ration of the condenser. If under these circum- FlG ,s correction collar to the lenses be apochromatic condenser. separated bi/ means of the collar adjustment, the black spots will be close*! u ^,, i/,»f a circularand evenly illinitiated disc will appear. This is a distinct , and will enable the
. The microscope and its revelations. that when thecondenser is racked the exteriorshape of the illuminatedportion will becomemore circular, two darkpatches will appear oneither side of the centre,showing the operationof the spherical aber-ration of the condenser. If under these circum- FlG ,s correction collar to the lenses be apochromatic condenser. separated bi/ means of the collar adjustment, the black spots will be close*! u ^,, i/,»f a circularand evenly illinitiated disc will appear. This is a distinct , and will enable the observer to see more than he couldI lave seen before. Mr. Kelson made this manifest on the examina-tion of a well-known diatom, Navicida major. If examined in its principal view, two vertical stripes will be seen running down thecentre of the hoop (fig. 243, «) ; these can easily be resolved intostride with a J--inch objective, but the probability is that these stria*are not the real structure but rows of minute perforations incom-.
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
