67 
means of association by which ideas can be combined, might 
serve the same purpose in the same manner, and that the same 
reasoning would apply; though he only considered it neces- 
sary to follow the inquiry with regard to the large class of 
accidental associations which are the main ground of the or- 
dinary work of memory. 
He next entered into an inquiry as to the comparative 
durability of the different classes of associations. This, he 
observed, must depend on their distinctness, and their cohe- 
rency: and hence he inferred that, generally, visible objects 
are the most easily recalled; and that certain combinations 
of sound might be next in order: after these might be 
reckoned the class of professional associations. He remarked 
upon the expedients used in the systems of artificial memory, 
as founded on this principle; and strongly condemned the 
methods, as being a substitution of false combinations, instead 
of those founded on the real relations of things. 
The Author then went on to apply his theory to some 
known phenomena in derangement, dreaming, &c.: and con- 
cluded with some general statements upon the sum of his 
results, and the progress he had made in his inquiry. 
A paper was read by Dr. Allman, containing a notice of 
two undescribed alge, which clothe the face of the rock over 
which the water trickles in the “ Dripping Well” of Knares- 
borough. They are referrible to the genus Microcystis, 
Menegh. 
Dr. Allman also noticed the occurrence in Ireland of the 
genus Phylactidum of Kutzing, which thus becomes an ad- 
dition to the British Flora. The beautiful little alga now 
noticed, which appears specifically distinct from P. elegans, 
Kutz., was discovered by Dr. Allman, during the autumn of 
1843, in a small, rapidly running rivulet near Bandon, in the 
County Cork. 
