m 
Natural Philosophy. — Hydrodynamics. 
Academy has undertaken a course of experiments, with a view 
to reduce to some law this new impediment to the perfec- 
tion of the art of navigation. The first course of experi- 
ments, which were carried on at the observatory of his friend 
the Reverend Mr Evans, is completed, and has given rise to 
many curious results : a new course is now going forward at 
the Royal Military Academy, but the experiments are too little 
advanced to say what new deductions can be made from them. 
In the first course, it appears that four out of the six chronome- 
ters employed, decidedly lost on their rates in every position near 
the iron, amounting in some cases to 4" or 5" per day. One 
chronometer seems to have gained in every position, and another 
was scarcely affected in its rate in a perceptible manner. Mr 
Barlow has ascertained that the power of the magnet in this case, 
as in his former experiments, resides wholly on its surface. We 
hope to be able to give a more particular account of these expe- 
riments in our next Number. 
13. Effect of Position on Magnetic Masses. — In vol. i. p. 242. 
of this Journal, we have mentioned the facts on this subject no- 
ticed by Colonel Gibbs. Sir Charles Giesecke observed simi- 
lar effects in Greenland. All the basalt of Disco Island is mag- 
netic. That which is found in the most elevated situations is 
most so, the fallen masses dispersed around the base of the 
mountains having more power over the needle than the others. 
HYDRODYNAMICS. 
14. Water Velocipede. — An exhibition, improperly called walk- 
ing on the water , has been exhibited in Scotland by Mr Kent. 
The apparatus which he uses is represented in Plate I. Fig. 18. 
where a, 6, c, are three hollow tin-cases of the form of an ob- 
long hemispheroid, connected together by three iron bars, at the 
meeting of which is a seat for the exhibitor. These cases, filled 
with air or some gas, are of such a magnitude that they can easily 
support his weight ; and as ah and ac are about ten feet, and he 
about eight feet, he floats very steadily upon the water. The feet 
of the exhibitor rest on stirrups, and he attaches to his shoes, by 
leather-belts, two paddles, d,e, which turn round a joint when he 
brings his foot forward to take the stroke, and keep a vertical 
position when he draws it back against the resisting water. By 
