288 Correspondence—Mr. G. E. Dibley. 
made in the tank. Mrs. Ayrton is explicit on this pomt. She says, 
and very truly, with reference to the tank, that ‘‘the sand has heaped 
itself up in the middle of the en having a contour very unlike 
sea-shore ripples.” (Abstract, p 4.) 
The paddle experiment uti the nearest approach to sea-shore 
conditions, but it is practically impossible to make oscillating waves 
of uniform period by hand, and a paddle is a most unsuitable 
instrument for the attempt. 
Had Mrs. Ayrton read a paper on so novel a subject in the usual 
way there would have been a most valuable discussion on it, as there 
were members present of both the British Association Committees 
that have investigated ripple-mark, viz., that on ‘‘ Waves and Currents 
in Estuaries” and that on ‘‘ Terrestrial Surface Waves and Wave-like 
Surfaces.” 
In a letter to the Magazine in December, 1904, I pointed out that 
all that was needful was a conference between Mrs. Ayrton, Sir George 
Darwin, Prof. Osborne Reynolds, and Dr. Vaughan Cornish, and that 
a unanimous report might easily be arrived at. Since then, however, 
the Royal Society have authoritatively approved Mrs. Ayrton’s views 
on the general subject of ripple-mark, and have thereby. inferentially 
disappr oved of the aforesaid eminent authorities. 
I only wish Mrs. Ayrton could be prevailed upon to experiment 
with waves of regular period running on a beach. The original 
suggestion was made by the late Mr. William Froude, F.R.S. My 
own small experiments did little, but they showed how much could be 
done with suitable tanks and motors to reproduce marine phenomena. 
eis Ielhospe, 
April 10th, 1907. 
UINTACRINUS IN THE LONDON BASIN. 
Sir,—It may interest your readers to know that I have at last 
found Utntacrinus in the London Basin, near Orpington. The 
specimens have been submitted to Mr. Sherborn, who writes: 
‘‘T have no hesitation in identifying your specimens as Uintacrinus, 
because you send me well-preserved plates as well as large and small 
arm-ossicles. Hearty congratulations; you have worked hard enough 
for the discovery of this zone.” Iam now engaged in working out 
the area of the exposure. G. E. Drsrey. 
April 23rd, 1907. 
OBITUARY. 
JOHN FRANCIS. WALKER, M.A., F.L.S.,. GGiSee Gas: 
We deeply regret to record the death of our valued friend and 
fellow-worker in geology for so many years, John Francis Walker, 
who died rather suddenly at his residence, 45, Bootham, York, on 
23rd May, aged 66. We hope to give a suitable notice of his work 
next month. 
