70 
MR. T. E. STANTON ON THE PASSAGE OF HEAT BETWEEN 
The apparatus being made, before more complicated experiments were tried, it 
was necessary to test the truth of the above assumption that, at velocities greater 
than the critical value for the pipe, the temperature at any cross section was constant 
at all points in the section, not immediately adjacent to the surface of the hot pipe. 
To test this, the pipe and jacket were fixed vertically, with hot Avater at about 
70° C. flowing up the jacket, and water at 20° initially flowing up the j^ipe. A cap 
was fitted to the end of the pipe, having a small pipe, of half the diameter of the 
outer one, projecting about 1 centim. into it, as shown in fig. 2. 
In this way the water at the section AB was divided, the inner portion passing into 
the chamber C, and the outer portion into the chamber D, in which the tempej-atures 
were taken by thermometers. 
It Avas found impossible to detect any difference in temperature betAveen the 
Avater taken from the centre of the pipe and that from the outside, and this even in 
cases when the velocity Avas considerably beloAV the critical value, thus shoAving 
that when the temperature of Avater flowing through a pipe is continually changing 
the motion is unsteady, even although the velocity is beloio the critical value. 
Fig. 2. 
T/ier/riomeCer _ 
This may be illustrated by the folloAving exjieriment. A glass jar, filled Avith 
Avater, and having a glass pipe fixed to it, as shoAvn in fig. 3, and through Avhich 
Avater may be drained, is alloAved to stand until the eddies in the water haAm 
died out. 
A tap is then opened at the bottom, and the Avater alloAved to floAV doAvn the pipe. 
If noAv a streak of highly-coloured Avater be alloAved to pass into the pipe from the 
