. The London, Edinburgh and Dublin philosophical magazine and journal of science . e second by increasing, by repeated re-flexion, the path of the light to about ten times its formervalue. The apparatus is represented in perspective in fig. 3, in planin fig. 4, and in vertical section in fig. 5. The stone a (fig. 5)is about 1*5 metre square and 0*3 metre thick. It rests onan annular wooden float bo, 1*5 metre outside diameter, 07metre inside diameter, and 025 metre thick. The float restson mercury contained in the cast-iron trough cc, 1*5 centi- 454 Messrs. Michelson and Morley on the Relative
. The London, Edinburgh and Dublin philosophical magazine and journal of science . e second by increasing, by repeated re-flexion, the path of the light to about ten times its formervalue. The apparatus is represented in perspective in fig. 3, in planin fig. 4, and in vertical section in fig. 5. The stone a (fig. 5)is about 1*5 metre square and 0*3 metre thick. It rests onan annular wooden float bo, 1*5 metre outside diameter, 07metre inside diameter, and 025 metre thick. The float restson mercury contained in the cast-iron trough cc, 1*5 centi- 454 Messrs. Michelson and Morley on the Relative Motion metre thick, and of such dimensions as to leave a clearanceof about one centimetre around the float. A pin d, guidedby arms g g g g, fits into a socket e attached to the float. Thepin may be pushed into the socket or be withdrawn, by alever pivoted at/. This pin keeps the float concentric withthe trough, but does not bear any part of the weight of thestone. The annular iron trough rests on a bed of cement ona low brick pier built in the form of a hollow octagon. Fig. At each corner of the stone were placed four mirrors dd ee,fig. 4. Near the centre of the stone was a plane parallel glassb. These were so disposed that light from an argand burnera, passing through a lens, fell on b so as to be in part re-flected to d{; the two pencils followed the paths indicated in thefigure, b d edbf and b d, ^^/respectively, and were observedby the telescope/. Both / and a revolved with the mirrors were of speculum metal carefully worked tooptically plane surfaces five centimetres in diameter, and theglasses b and e were plane parallel of the same thickness,1-25 centimetre ; their surfaces measured 5*0 by 7*5 centi-metres. The second of these was placed in the path of oneof the pencils to compensate for the passage of the otherthrough the same thickness of glass. The whole of theoptical portion of the apparatus was kept covered with awooden cover to prevent air-currents a
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Keywords: ., bookcentury1800, bookdecade1840, bookidlondon, booksubjectscience
