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motes dancing in a sunbeam the particles of dust floating in the air of the room, 
but only visible where the entering ray of light falls athwart them. 
in this connection the recent deep sea soundings of the Challenger have 
brought to light a curious fact. Sir Wyville Thomson found that beds of sediment 
were being slowly formed on the deepest ocean floors, but so slowly was the rate 
of deposition made that it has been compared to the fall of dust in an unoceunied 
room. No better proof of thiscan be given than that an examination of the abyssal 
mud disclosed the presence of an appreciable proportion of meteoric iron the 
product of those falling stars which dissipate themselves on entering our atimos- 
here. Professor Geikie says in a recent geographical lecture in Scotland “ to. 
earn that mud gathefs there so slowly that the very star dust forms an appreci- 
able part of it, brings home to us as hardly anything else could do, the idea of 
undisturbed and slow accumulation.” 
An interesting memoir by M. Tschermak, of the University of Wissen- 
chaften was published in 1875 on thesource of meteoroids, and a paper on his 
memoir was last year read before the Royal Irish Academy by Mr. Robert Ball. 
Techermak claims a volcanic source in some celestial body. Mr. Ball follows 
the theory further, and by able reasoning shows that if ejected from the planets 
or asteroids there would only be a chance of one in 50,000 of them falling on the 
earth. If in the early stage of our own earth’s history, long anterior to life, when 
mighty convulsions were rending it, colossal volcanoes may have existed with 
explosive energy enough to drive missiles upwards with a velocity which would 
carry them far enough from the earth to a point where they would continue to 
move in orbits round the sun, crossing at each revolution the point of the earth’s 
track from which they were originally discharged— if this were the case there are 
now doubtless myriads of these projectiles moving through the solar system, the 
only common feature of whose orbit is that they all intersect the track of the 
earth, and it and they now and then meeting, the point of intersection would be 
marked by the desent of a meteorite. This theory was hinted at by Dr. Phipson 
in a work published by him in 1866, and Mr. Lawrence Smith, another later 
writer on this subject inclines to the same view. No volcano now exists with 
explosive energy enough to eject fragments that could constitute future meteoroids 
and if such ever did exist, it could only bein the early stages of the earth’s history. 
Another and an ingenious thecry advanced by Professor Newton of Yale 
College, and one meeting with general acceptance, is that meteoroids are fragments 
of or attendants on a comet, and in a lecture of his in 1879 he scientifically 
endeavors to prove this. Speaking of the recurring November meteoric showers: 
which manifest themselves at their maximum every thirty-three years, 
he says vast masses of these small bodies move in a long thin stream 
around the sun, and the earth at stated times plunges through them taking- 
with its atmosphere each time scores of millions of them. Their orbit is 
described in thirty-three and a quarter years. They go out a little 
farther than the planet Uranus or about twenty times as far as the. 
earth is from the sun. While they all describe the same orbit they are not 
collected in one compact group, but taking four or five years to pass a given 
point in the orbit, they may be likened to a train several hundred million of miles 
long, but only a few thousand in thickness. Along with this train travels a 
comet. Every August, about the tenth of the month, there is another star 
sprinkle or slighter display of meteors (known amongst the common people as St. 
Lawrences’ tears) and a comet whose period is 125 years, moves in the plane: 
with these meteors and in a like orbit. Again early in December there are star 
showers, the meteoroids composing them travelling in tke orbit of Biela’s comet. 
In April slight showers again occur, conuected with another comet’s orbit. The 
