HenneSSY— On Floatation of Sand by the Rising Tide. 153 
present discussion. Besides, it is altogether gratuitous, and inconsistent 
with scientific reasoning, to assume that the crinoidal in-filling ''is 
similar to that effected by the ancient serpentine of the Laurentian " 
(Dawson) ; or, that it is allied in the mode of its formation to the 
serpentine, pyroxene, and other minerals which have injected Eozoon" 
(Sterry Hunt). 
The other relates to our statement of the occurrence of an essential 
" eozoonal feature" in connexion with a crystal of spinel, from Amity. 
We now learn that Dr. Dawson has had under examination specimens 
of spineliferous rock from the latter place: — and, notwithstanding his 
having pronounced the case as "50 unlihehj^^ the result is, that the 
specimens have been found to contain in spots, remains of casts of 
canals similar to those of Eozoon Canadense^ As to the inference that 
the specimens are portions of a bedded rock, and not a vein stone" — 
without taking into consideration that it is suppositional, and based on 
an examination of specimens preserved in collections — it cannot set aside 
the plain fact, that in our specimen arborescent configurations — formed 
of groups of decreted crystals of malacolite, and identical with perfect 
and the finest examples of what are presumed to be '' casts of the canal 
system" — are present in calcite, occupying the crevices of a large 
crystal of spinel. The fact of itself conclusively settles their purely 
mineral origin. 
XXY. — Oi^ THE Eloatation of Sand by the Rising Tide m a Tidai; 
EsTUAEY. By Pkofessoe Hennessy, E. R. S., Vice-President of 
THE Academy. 
[Eead April 10, 1871.] 
DuEiNG the course of a tour along our western coast, in the summer of 
1868, the following incident came under my notice : and, although I 
made a note of the facts at the time, I have never hitherto made them 
the subject of a scientific communication : — 
On July 26, when approaching the strand at the river below the 
village of l^ewport. County Mayo, I noticed what appeared to be exten- 
sive streaks of scum floating on the surface of the water. As it was 
my intention to bathe, I was somewhat dissatisfied with the appearance 
of the water, until I stood on the edge of the strand, and I then per- 
ceived that what was apparently scum, seen from a distance, consisted 
of innumerable particles of sand, flat flakes of broken shells, and the 
other small debris which formed the surface of the gently- sloping 
shore of the river. The sand varied from the smallest size visible to 
the eye up to little pebbles, nearly as broad and a little thicker than 
a fourpenny piece. Hundreds of such little pebbles were afloat around 
me, and it is probable that the flakes of floating matter seen farther oif 
contained also a considerable proportion. The air during the whole 
K. T. A. TROC—VOL. 1., SER. II., SCIENCE, 
X 
