341 
and F unctions of the Sponge. 
the empty tubular fibers of the S. communis. The fibres of this 
last species, when highly magnified, resemble the empty stems 
of dead sertularise, from whose central axis the granular matter 
has been washed out, or consumed by animalcules, while the fibres 
of the two former species resemble the stems of living sertularise, 
whose central cavity is always filled with soft, moving, granular 
bodies. 
Art. XX. — A concise Statement of the Magnetical and other 
Philosophical Experiments and Observations made during 
the recent Northern Expedition under Captains Parry and 
Hopner 1824-5. By a Correspondent. 
It was stated in our last Number, that the papers containing 
the detail of the above experiments were in the hands of the 
Admiralty. They have since been laid before the Royal Society, 
by whom they are expected to be published, forming an addi- 
tional part, as was done last year in the case of Messrs Herschel 
and South’s paper, containing their observations on the Double 
Stars. The expence of both being defrayed by the Board of 
Longitude. 
The first and most extended paper is by Lieutenant Foster, con- 
taining a detail of his observations on the length of the seconds’ 
pendulum, with the instrument which Captain Sabine employed in 
the numerous observations he made in various parts of the nor- 
thern hemisphere. The nature of these observations is too well 
known to require any description of them in this place ; but with 
respect to the observer, it may he proper to state, that he is the 
gentleman who accompanied and assisted Captain Basil Hall in 
his interesting voyage to the western coast of America, and who 
afterwards assisted Captain Clavering in his voyage to Spitzber- 
gen and the eastern coast of Greenland, and whose accuracy 
as an observer, and indefatigable exertions, in every scientific 
pursuit, cannot fail henceforward to place his name amongst 
the most distinguished scientific navigators of England *. 
* We are glad to learn that Lieutenant Foster is at present engaged in pre- 
paring for another scientific voyage to the southward. He will accompany Cap- 
tain King in the Endeavour. 
