210 THE SPLASH OF A DROP AND ALLIED PHENOMENA. 



In tlie subsequent figures it will be noticed that the arms which are 

 thrown up at first afterward segment into drops which tly ott" and sub- 

 side (fig. 8), to be followed by a second series whicli again subside 

 (fig. 11), to be again succeeded by a third set. In fact, so long as there 

 is any downward momentum the drop and the air behind it are pene- 

 trating the li(piid, and so long must there be an upward flow of dis- 

 placed liquid. Much of this flow is seen to be directed into the arms 

 along the channels determined by the segmentation of tlie annular 

 rim. This reproduction of the lobes and arms time after time, on a 

 varying scale, goes far to explain the puzzling variations in their 

 number which I mentioned in connection with the drawings. I had 

 not, indeed, suspected this, which is one of the few new points that the 

 photographs have so far revealed. 



With respect to these photographs,' the credit of which I hope you 

 will attribute, first, to the inventors of the sensitive jjlates, and, second, 

 to the skill and experience of Mr. Cole, I desire to add that they are, as 

 far as we know, the first really detailed objective views that have been 

 obtained with anything approaching so short an exposure. 



Even Mr. Boys's wonderful photographs of flying bullets were after 

 all but shadow photographs, and did not so strikingly illustrate the 

 extreme sensitiveness of the plates, and I want you to distinguish 

 between such and what (to borrow Mr. F. J. Smith's phrase) I call an 

 "objective view." 



It remains only to speak of the greater irregularity in the arms and i 

 rays as shown by the photographs. The point is a curious and inter- 

 esting one. In the first place, I have to confess that in looking over 

 my original drawings I find records of many irregular or unsymmet- 

 rical figures, yet in compiling the history it has been inevitable that' 

 these should be rejected, if only because identical irregularities never 

 recur. Thus the mind of the observer is filled with an ideal splash — 

 an "auto-splash" — whose perfection may never be actually realized. 



But in the second place, when the splash is nearly regular it is very 

 difiicult to detect irregularity. This is easily proved by projecting on i 

 the screen with instantaneous illumination such a photograph as that 

 of Series X, fig. G. My experience is that most persons pronounce what : 

 they have seen to be a regular and symmetrical star-shaped figure, and 

 they are surprised when they come to examine it by detail in continuous 

 light to find how far this is from the truth. Especially is this the case • 

 if no irregularity is suspected beforehand. I believe that the observer, , 

 usually finding himself unable to attend to more than a portion of the 

 rays in the system, is liable instinctively to pick out for attention a part 



1 Three of these photographs, viz, Nos, 11, 12, and 17, are reproduced full size 

 (Plate XVI) hy a photographic process, to euahle the reader to form a more correct 

 idea than can be gathered from the engravings of the amount of detail actually 

 obtained. The black streaks seen in figs. 11, 15, 16, and 17 are due to particles of 

 lampblack carried down by the drop from the smoked surface on which it rested, 



