Word: plate
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Dates: during 1890-1899
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After the debate there will be a banquet at the Empire Cafe, Boston, to which members of the three debating clubs are invited. The price per plate will be $2.50. Those intending to attend should hand their names to R. C. Davis, 20 Ware Hall. Among those who have signified their intention of being present are ex-Governor J. D. Long, ex- Governor William E. Russell, Acting Governor Roger Wolcott, and President Eliot...
After the experiment was finished Professor Trowbridge explained that the same light can be produced with a common electric machine, but the plate must be exposed an hour when this machine is used. This shows how simple the process really is. The chief advantage of the large apparatus is that when it is used only a minute's exposure is necessary. The distinguishing character of the cathode rays is that they do not go between the two poles. They can be thrown any way. For instance, a small piece of aluminum can be used to throw them in any direction...
Coming now to the method of taking photographs, the lecturer showed the difference in the process. In taking a photograph with cathode rays a plain dry plate is used. There are the customary slides in the holder but there is no central opaque partition. The hand or object to be photographed is put on the slide and you get a photograph of the shade. As glass absorbs the rays a lens would be of no use and would prevent the taking of a photograph. Thus the common process of photographing is exactly reversed with the cathode rays. This was illustrated...
Cathode photographs have been called shadow pictures, but this is not an exactly correct name for them. This is because a piece of glass as thick as a piece of paper absorbs a large number of rays and throws a very thick shadow on the plate while even a thick piece of wood throws hardly any shadow. The shadow photograph, however, is very exact in other respects. In the photograph of the human hand it shows the gradations of the absorption of the rays with the thickness of the bones...
Distance of the object from the plate plays a big part in cathode photography. The successful photographs of the human hand have been those where the palm was facing the cathode, which put the bones nearer the plate by a very little. The greatest interest in the experiments is because of its application to surgery. Glass can be easily detected in the hand and in the foot...