. The Locomotive. well to explain that although the experimental tubehad different temperatures in its different parts, yet the pressure of the vapor, solong as no air was present, and so long as ED was the coldest part of the tube,depended solely upon the temperature at ED. When G is warmer than E, thevapor at G is superheated, while that at E is just saturated; but the pressure i9oS.] THE LOCOMOTIVE 59 is the same throughout the tube, and is determined by the temperature at ED.)The readings of the gage, KFG, were taken by means of a telescope, whichwas rigidly fixed, and placed so that the u
. The Locomotive. well to explain that although the experimental tubehad different temperatures in its different parts, yet the pressure of the vapor, solong as no air was present, and so long as ED was the coldest part of the tube,depended solely upon the temperature at ED. When G is warmer than E, thevapor at G is superheated, while that at E is just saturated; but the pressure i9oS.] THE LOCOMOTIVE 59 is the same throughout the tube, and is determined by the temperature at ED.)The readings of the gage, KFG, were taken by means of a telescope, whichwas rigidly fixed, and placed so that the upper ends, or meniscuses, of the twomercury columns could both be seen in the field of view of the telescope at thesame time. The telescope was provided with a micrometer eyepiece, whoseerrors were carefully investigated, and whose screw had been standardized byobservations made upon a standard centimeter scale, placed in the exact posi-tion subsequently occupied by the mercury gage. The difference in level of the. Fig. 2. — Showing the Experimental Tube Filled and in Position. mercury in the two arms of the gage was obtained by turning the screw of themicrometer eyepiece so that the cross-hair rested first on one of the meniscuses,and then on the other. By the side of this telescope there was a second one,through which the readings of the thermometers TT were taken. Juhlin considered the possible errors of his apparatus with much example, he constructed a separate apparatus, with which he made numerousobservations to see if any correction was needed on account of the differencein the pressure of the mercury vapor in K and in ECG, due to the fact that the 60 THE LOCOMOTIVE. [April, temperature at E is lower than that at K; but we do not need to discuss of the research, because he found that the error arising from omittingthis correction was insignificant. He applied the usual correction, however, toreduce the readings of the mercury gage to the values they
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Keywords: ., bookauthorhartfordsteamboilerin, bookcentury1800, bookdecade1860
