22 ; REPORT—1857. 
the author was illustrated by another diagram, in which a succession of seven equal 
alternate applications of positive and negative force following a first impulse of half 
strength, was shown to give seven turns of the tide at the remote end, and there- 
fore eight motions of the relay, following one another at not very unequal intervals 
of time. 
Outline of a Theory of the Structure and Magnetic Phenomena of the Globe. 
By J. DRumMMonp. 
The author, from the admitted fact of our earth having cooled down from an 
original state of fluidity, and that it now is a solid crust enclosing a fluid mass of 
molten materials, held that there must be an action of the sun and moon on this 
fluid mass analogous to that which caused the tides of the ocean; that from thence 
an outward pressure on the crust must result, propagated along it, in a manner 
similar to the great tidal wave; and from this principle, in an elaborate essay, he 
deduced the ordinary magnetic phenomena, as well as volcanoes, earthquakes, and 
other violent actions; concluding by answering objections which may be urged 
against the foundation and details of this theory. 
Magnetic Experiments made on board the ‘ Great Eastern’ Steamer. 
By W. Runve.y. (Communicated by Admiral FitzRoy.) 
Admiral FitzRoy exhibited to the Section, and explained tables and a diagram, 
showing the deviations observed in a compass placed successively at each of eight 
stations along the deck of the monster iron vessel now building at Millwall. 
Sounp. 
On a singular Acoustic Phenomenon. By M. Donovan, M.R.LA. 
The author explained the beats which are experienced when two strings tuned 
nearly, but not exactly, to unison, are struck at the same time. He then stated 
that Earl Stanhope had observed these beats in all the tuning-forks tried by him, 
which he attributed to inequality of the prongs. Earl Stanhope, in consequence, had 
been at the pains to invent a new tuning instrument. This effect the author often 
tried to experience, but vever could succeed until upon one occasion, just after he had 
ceased from violent exercise, having applied the fork to his teeth, he distinctly heard 
the beats. He was thus led to the true origin of the phenomenon, which he could 
now experience whenever he wished, by running a short distance, particularly up and 
down stairs. ‘The effect was caused by the beatings of his own heart, which are 
synchronous with those of the fork. 
On the Effect of Wind on the Intensity of Sound. 
By Professor G. G. Sroxes, M.A., D.C.L., Sec. RS. 
The remarkable diminution in the intensity of sound, which is produced when a 
strong wind blows in a direction from the observer towards the source of sound, is 
familiar to everybody, but has not hitherto been explained, so far as the author is 
aware. At first sight we might be disposed to attribute it merely to the increase in 
the radius of the sound-wave which reaches the observer. The whole mass of air 
being supposed to be carried uniformly along, the time which the sound would take 
to reach the observer, and consequently the radius of the sound-wave, would be in- 
creased by the wind in the ratio of the velocity of sound to the sum of the velocities 
of sound and of the wind, and the intensity would be diminished in the inverse 
duplicate ratio. But the effect is much too great to be attributable to this cause. 
It would be a strong wind, whose velocity was a twenty-fourth part of that of 
sound; yet even in this case the intensity would be diminished by only about a 
