453 



Prof. Guthrie on Drops. 



[Recess, 



on the whole, the sizes of the drops at the slower rates are less influenced 

 by equal increments of gt than are those of the quicker rates. This, how- 

 ever, only appears distinctly at and below the rate of about fft=V''00. 



If the connexion between gt and the drop-size be represented by a curve 

 (fig. 2, A), the abscissae being the values of fft, and the ordinates the 

 corresponding drop^weights, there is apparently no asymptote parallel to 

 the axis of X. The curve presents, however, in its course two secondary 

 maxima and minima : 



Secondary maxima. Secondary minima. 



(1) fft =-450" fff='433" 



(2) f<{=..5,7" fft=-467" 



Although at these minima the drops are less than at the immediately 

 succeeding rates, yet the quantity of liquid passed in a given time is, at 

 every rate of dropping, greater than the quantity passed in the same time 

 at every slower rate. The decrease of rate more than counterbalances the 

 temporary increase in the drop-size. This is seen on comparing the num- 

 bers of column 3, Table IV., with one another. They are found to de- 

 crease continually, though by no means uniformly, as the rate of dropping 

 decreases. The same fact is shown graphically in fig. 2, B. 



The second maximum (at fft =*500 and gt ='5l7) is in remarkable 

 connexion with the rate at which a series of drops may be converted into 

 a continuous stream. At all rates of dropping, from ^^=-333 to gt='5\7 

 inclusive, the drops may be converted into a permanent stream by pouring 

 a little additional oil upon the sphere as the drops are falling from it. A 

 stream is thus established which remains for any length of time, if it be 

 protected from all currents of air and vibration. At the rate ^^='519 

 the stream may be established by the same means for a few seconds (about 

 30"), but the continuous part inevitably begins to palpitate, becoming 

 alternately longer and shorter, thinner and thicker, until at last it draws 

 up and is converted into a succession of drops. At the immediately slower 

 rates of dropping the same effect follows, but in each case in a shorter 

 time, so that the slowest rate of dropping, which may be converted into 

 permanent running, coincides with the rate which gives the second maxi- 

 mum size of drops (^^=*500 and gt='^\7). The appearance of a drop- 

 convertible stream is peculiar, the narrowing which it undergoes on leaving 

 the solid being remarkably sudden. 



:^:In many liquids such secondary maxima are entirely wanting. They 

 appear in liquids of the physical nature of oils, whether those oils be che- 

 mically fatty (adipic saltjof glycerine), or whether they be miscible with 

 water, as syrups, glycerine itself, &c. 



In order to avoid the influence of variations in rate, we shall for the 

 future take the same rate of dropping in all cases, and, unless the contrary 

 be stated, the rate adopted will be ^^=2". 



