MR, C. A. BELL ON THE SYMPATHETIC VIBRATIONS OE JETS. 
411 
If the jet liquid be coloured the analogy becomes strikingly evident. At low pressures 
the continuous part of the stream of coloured liquid is elongated and unsteady, being 
easil} r swayed about by currents in the surrounding liquid : and where it becomes 
discontinuous it either branches or forms a divergent cone. In this condition it is 
not sensitive to sounds of high pitch ; but a musical tone of low pitch, or a gentle tap 
on the supporting sound-board, causes it to break quite close to the orifice. As the 
pressure is increased the breaking point first recedes from and then approaches the 
orifice ; and when the velocity is so great that the jet visibly responds to high tones, 
the continuous portion, even of a jet 1 mm. in diameter, is little more than a centimeter 
in length. At the breaking point the liquid then spreads out as a divergent cone, 
quite similar to the conical brush seen on the end of a smoked air-jet. 
Fig. 10. 
We have seen that very little sound results from the impact of a vibrating air-jet 
against a membrane : and precisely the same is true for a jet of water when both jet 
and membrane are submerged. But the telephonic experiment last described shows 
that increased effects result when the receiving surface is so small as only to be 
affected by changes occurring in the neighbourhood of the jet axis. 
The analogy may be pushed further. If the velocity of the stream at different 
points be measured by introducing into its path a capillary tube connected with a 
vertical tube containing either mercury or water, which may serve as a manometer, a 
progressive fall in velocity will be indicated as the manometer orifice is moved away 
from the jet orifice and along the axis ; and a similar fall in velocity as the manometer 
orifice is moved from any point on the jet axis radially towards the circumference. 
The diminution in the latter case is steeper near the orifice than at a distance from it, 
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