187 
while gladly acknowledging the great mathematical learning 
and originality exhibited in that and every paper by Mr. 
Cayley, Sir W. Rowan Hamilton thinks it right to state, 
that he was led to his own results, respecting the relation 
(above assigned) between ten points on the surface of the second 
order, not by any system of co-ordinates, but by considerations 
of vectors, and by seeking to extend to ellipsoids the results 
respecting cones, which he had submitted to the Academy in 
July, 1846, and had also published in the Philosophical Maga- 
zine for the following month, as derived from the Calculus of 
Quaternions. 
Mr. M. Donovan handed in a paper on a new and singular 
acoustic phenomenon produced by tuning-forks. 
Mr. David Moore, Curator of the Royal Dublin Society’s 
Botanic Gardens, communicated the following details of the 
results of physiological experiments on the formation of wood 
in plants, made in the Royal Dublin Society’s Botanic Gardens, 
Glasnevin, between the years 1839 and 1851:— 
‘‘ It may appear remarkable in vegetable physiology, that 
what has long been considered an axiom should now be 
gravely disputed by one of the best physiologists of the present 
time. Dr. Schleiden, of Jena, in his admirable work, ‘ Prin- 
ciples of Scientific Botany,’ flatly denies that a downward 
current of elaborated bark-sap either does or can take place 
in plants, which opinion gives to the experiments I propose to 
describe much additional interest. At the time my experi- 
ments were commenced, and for several years afterwards, the 
descent of the sap in vegetables does not appear to have been 
doubted, the whole theory of wood-formation resting on the 
fact of such being the case. It was, therefore, more with a 
view of eliciting information on the latter subject, than to 
