Word: prism
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Dates: during 1900-1909
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...would injure certain channels of the harbor, but in opposition to this contention several of the most eminent engineers of the state have expressed the opinion that the tidal scour theory has no application to the conditions which exist in those channels of Boston Harbor over which the tidal prism of the Charles river Basin moves...
There are two other stationary instruments. Over the end of one a prism is placed, which breaks up the light of the stars so that by the study of the rays the composition and character of any one star may be accurately determined. The second instrument is regulated by two ordinary alarm clocks, which open and close the shutter at any time the operator may wish. Every night this telescope is pointed directly at the north star, and after an exposure of twelve hours a semi-circle is thus traced on the plate. By this device an impression...