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substance. In tbe solution there were produced sulphite and phosphite, 
hyposulphite and hypophosphite, and slight traces of sulphate and phosphate 
of potassium. At the end of three months the conditions were still much 
the same ; the phosphorus was still fluid and mobile, the sulphur more 
eroded, the same products present in solution, though increased in quantity 
and somewhat altered in the ratio which the one salt bore to the other ; due 
allowance being made for increase, the proportion of sulphate and phosphate 
was greater. The electricity which was subsequently proved to be developed 
was found to be greater than that produced by an ordinary Daniells cell, and 
it lasted for more than three months. 
The Colour of Fluorescent Solutions. — Dr. H. Morton has sent to a late num- 
ber of Silliman’s “American Journal” a paper describing experiments of his 
which sustain the interesting conclusion that “ all the familiar fluorescent 
solutions, such as the tinctures of turmeric, of agaric, of chlorophyl, and 
the solution of nitrate of uranium, emit lights of the same colour of 
fluorescence — namely, blue, identical with that developed by acid salts of 
quinine.” 
The Mode of Production of the Aurora Borealis. — An important paper, by 
Herr Zollner, in which those who are engaged in spectroscopic inquiries will 
be interested, appears, in Poggendorff ’s “ Annalen ” (cxli. p. 574). After 
some preliminary discussion, he says that a layer of ignited air l m in thick- 
ness would, at a height of ten miles, be equivalent to a pressure of 78 mm , 
and at a height of twenty miles, to a pressure of O01 mm in a Geissler’s tube, 
in order at the same temperature to give a spectrum as bright as that of the 
aurora. But as the thickness of the layer of ignited air must be reckoned 
by kilometers instead of meters, we should have, even at a height of ten 
miles, so high a value for the equivalent pressure in a Geissler’s tube — 78 m 
of mercury for a layer 1 kilometer in thickness — that the most powerful 
induction apparatus could not overcome the resistance of the air. From 
this it follows that the quantity of particles of ignited air in a Geissler’s 
tube is probably extremely small when compared with the active quantity 
in the case of the aurora. Since, however, the spectrum of a gas in such a 
tube must have at least the brightness of the auroral spectrum to admit of 
spectroscopic analysis, it follows that the emissive power of the particles of gas 
ignited in the tube must be much greater than that of the ignited gaseous 
particles in the case of the aurora. Such a' difference can be produced only 
by differences in temperature. If, therefore, the light of the aurora depends 
on ignited particles of our atmosphere, the temperature at which the igni- 
tion takes place must be much lower than that at which the same gases 
can be ignited by electricity in Geissler’s tubes. From these considera- 
tions it appears that all the gas-spectra of the different orders which we 
can artificially produce belong in general only to high temperatures, since 
the relatively greater brightness with less quantities of ignited matter ren- 
ders a greater emissive power necessary, and this can be produced only by a 
higher temperature. Conversely, as in the case of the aurora, corona, 
zodiacal light, &c., a great number of active luminous particles must be 
assumed to exist, it follows that the temperature of the ignited gases must 
be relatively low. 
A New Mode of Producing Stereoscopic Effect. — The following account 
