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safely do so. “On the -whole,” he said, towards the close of the interesting 
paper which he read before the Astronomical Society on Friday, June 13, 
“ it does not seem improper for me to take the ground that having shown 
by photographs that the bright lines of the oxygen-spark spectrum all fall 
opposite bright parts of the solar spectrum, I have established the probability 
of the existence of oxygen in the sun. Causes,” he proceeded, “that can 
modify in some measure the character of the bright parts of the solar spec- 
trum, obviously exist in the sun, and these, it may be inferred, exert influence 
enough to account for such minor differences as may be detected.” In 
closing his paper, Professor Draper called attention to some points indicating 
the amount of labour and time his researches have already consumed. Each 
photograph demanded an exposure of fifteen minutes, and with preparation 
and development at least half an hour was needed. The making of a photo- 
graph, exclusive of experiments, required therefore about 30,000 10-inch 
sparks — that is, 30,000 revolutions of the bobbin of the Gramme machine. In 
the last three years the Gramme has made 20,000,000 of revolutions. The 
petroleum engine only consumes a couple of drops of oil at each stroke •, 
and yet it has used up about 150 gallons. Each drop of oil produces two 
or three 10-inch sparks. “ It must also be borne in mind,” said Professor 
Draper, “ that comparison spectra can only be made when the sun is shining, 
and clouds therefore are a fertile source of loss of time.” 
Mira Ceti . — This star reached its maximum about October 20 last. But 
an observation made by Mr. Greely of Boston, about three months before 
this time, would seem to show that there then occurred a well-marked 
though subordinate maximum. About the middle of August, Mr. Greely 
early in the morning, in looking for Saturn through the clouds, saw a star 
which he for a moment mistook for the planet ; but its scintillations soon 
showed that it was not Saturn, but something unusual in that quarter of the 
sky. The clouds cleared off soon after, giving him an opportunity of noting 
its brightness, which he says was fully equal to that of any second magni- 
tude star. Being curious to know what this star was, he carefully 11 memo- 
rized ” its position (such is the expression used by Professor Sawyer ot 
Cambridge, Mass., in describing Mr. Greely’s observations) — the word memo- 
rize is not perhaps to be found in the dictionaries, but “ ’twill serve.” On 
reaching home, Mr. Greely, by means of a star-chart, identified the star as 
being Mira. The next few nights were cloudy; and when he again saw the 
star it had greatly decreased in brightness, and shone as a fourth or fifth 
magnitude star. Professor Sawyer and Mr. Chandler (an observer of variable 
stars), were at first disposed to place little reliance on this singular observa- 
tion, not questioning Mr. Greely’s statements, but doubting if he had really 
identified Mira. Subsequent inquiries satisfied them however that he had. 
If the variations of Mira always followed the ordinary course described in 
the books, we could not very readily believe that on this particular occasion 
the star had deviated from its normal series of changes. But as a matter 
of fact abnormal phenomena have already been noted which tend to render 
Mr. Greely’s statement far less improbable than it might otherwise be con- 
sidered. Thus in the four years 1672 to 1676, Hevelius, though he searched 
specially for the star at the times when it should have shone with its 
maximum brightness (about that of a second magnitude star), failed alto- 
gether to detect it. 
