. The London, Edinburgh and Dublin philosophical magazine and journal of science. meter. The gasometer having been drawn up wrasset free ; when it had reached a more or less constantvelocity, the gauge was opened and the line kept on thecross wire either by accelerating or retarding the gasometerby means of the handle H. The experiment was then repeated with the pressure gaugecommutated. After a little practice it was generally possible to keep the the Value of the Phot Constant. :57 gasometer at the right velocity for the greater part of itsfall, and the required rate of this wns given by the
. The London, Edinburgh and Dublin philosophical magazine and journal of science. meter. The gasometer having been drawn up wrasset free ; when it had reached a more or less constantvelocity, the gauge was opened and the line kept on thecross wire either by accelerating or retarding the gasometerby means of the handle H. The experiment was then repeated with the pressure gaugecommutated. After a little practice it was generally possible to keep the the Value of the Phot Constant. :57 gasometer at the right velocity for the greater part of itsfall, and the required rate of this wns given by the averagedistance between the seconds marks on the paper strip. Determination of Kj.—Having determined by the processof trial and error the distribution of pitot pressure across adiameter for a given mean rate of flow, the value of Kj atthat velocity can be determined from curves drawn with\/P as ordinates and positions of the pitot along a radius asabscissae, as mentioned above. Some examples of these aregiven in Curves II for mean velocities 400, 120, and 50 cms. Curves 2D >»v£ R>Stt£o>v of Pitot per second respectively, P being measured in centimetres ofwater. The values for the ordinates of w = 120 and y=50are doubled and trebled respectively for convenience inplotting. The pitot in these cases was a circular metal tube ofradius 0*59 mm. The results verified the general form of 358 Messrs. J. D. Fry and A. M. Tyndall on the curve given by crosses in Curves I, and it appeared,therefore, that assuming that there was a source of error inthe original work with this method, it had not been being desirable to check these readings in some way,attempts were made to obtain them at still lower meanvelocities when the motion in the pipe would no longer beeddy bnt stream line. With stream-line motion the distribution of velocity acrossa diameter is parabolic. Assuming then that K is constantand of value lOO (as obtained by the centrifugal method),the
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectscience, bookyear1840
