146 
PROFESSOR A. M. WORTHINGTON AND MR. R. S. COLE 
The sphere has passed below the surface, yet this is almost undisturbed, and there is 
no trace of the equivalent quantity of dis[daced liquid. Indeed, in Photograph No. 9 
(as in Photograph No. 3 of Series V.) there is an indication of a slight depression 
surrounding- the small column. The conclusion we arrive at is that the general level 
of the whole liquid surface rises simultaneously with the entry of the sphere, or, at 
any rate, after an interval corresponding to the velocity of sound through the liquid. 
Direct evidence of this will be given later. But the surface, though undisturbed, is 
no longer the surface of dead liquid. Already in Photograph No. 9, and in the 
corresponding Photograph No. 3, of the next series, there are traces of convergent 
radial stream lines, indeed, the slight depression is itself evidence of velocity; in 
Photograph No. 10, after a relatively long interval, the base of the column has 
gathered liquid, and Nos. 11, 12, and 13, wdiich are coincident in point of time, show 
the very considerable column that subsequently rises (No. 13 probably owes its double 
column to some such antecedent condition as is shown in Photographs 5 and 6). 
Photographs 15 and 16 show the curious and characteristic manner in which this 
column topples over, while No. 17 shows how it occasionally succeeds in attaining a 
more considerable height. 
Series V. (Plate 5) shows the similar splash of a rather smaller stone sphere, 
1’5 centim. in diameter, falling through the same height of 60 centims. Examination 
of No. 2, wdth a lens, shows how, on the front side, the sheath (owing, no doubt, to 
imperfect polishing) has been driven away from the surface of the sphere, while at 
the back it has run up almost to the vertex. Of this splash we recorded that 
‘•'bubbles were heard.” Photographs 4 to 9'“ are all characteristic of the manner in 
which the column breaks up or topples, and appear to deserve record, if only to help 
future observers in what is sometimes a rather puzzling identification. 
Series VI. (Plate 6) was taken with a large stone sphere 3‘2 centims. in diameter, 
falling only 14 centims. (scale f linear), with a view to obtaining further information 
about the displaced liquid. In Photograph No. 1, the plate w^as accidentally exposed to 
a spark beforehand. No. 2 shows very well the rise of the sheath. No. 4 is interesting 
as illustrating in a very complete manner the influence of some slight roughness on 
one side only. The puckering of the surface, which is strongly marked in No. 5, 
seems to us to show that lines of flow near the surface wdien once determined are 
very persistent, for w^e should otherwise expect to find a gradual thickening of the 
sheath as the vertex is approached, but not these separate radial streams. In No. 6 
the general surface is very level, wdiile the amount of liquid in the column can hardly 
be of the volume of the whole sphere. It still remained, however, just doubtful 
wdiether a very gradual sloping-olf of the surface might not provide, in a manner not 
easily noticed, accommodation for a large amount of liquid just round the place of 
impact. We, therefore, choosing the narrower vessel of No. 8 to make the pheno¬ 
menon more apparent, filled it brim-full and placed the lower edge of a card 
* Tlie ilavk streak on the left side of No, 9 is an accidental flaw on the plate. 
