678 
POPULAE SCIENCE EEVIEW. 
Mr. Tichebome says, “ I am inclined to think the idea that a well-developed 
cube must contain iodide will be found to be altogether erroneous.” 
Wavy Lines on the Plxde. — To obviate the tendency which some collodions 
have to form wavy lines when the plate is coated, the editor of the 
American Journal of Photography recommends the addition of chloroform, 
in the proportion of ten drops to the ounce. He says it is effectual, but we 
cannot say why it should be so. 
PHYSICS. 
The nature of the Light Emitted by burning Magnesium has been recently 
investigated by Professor Schrotter, and his experiments published in a com- 
munication to the Vienna Academy of Sciences. M. Schrotter has obtained 
some important results, of which the most interesting are as foUows : — The 
magnesium light promptly and powerfully produces fluorescent as weU as 
photographic effects. This light contains an extraordinary quantity of ultra- 
violet rays, the spectrum of which is at least six times as long as that of the 
luminous portion. Crystallized platino-cyanide of barium, flnely powdered 
or made into a paste with gum, so that it can be flxed on paper, gives a 
powerful fluorescence when exposed to this light. All substances which be- 
come luminous by insulation acquire this property in the highest degree by 
a few seconds’ exposure to the burning magnesium, whilst with the sun it takes 
from five to ten minutes to produce the same effect. The light re-emitted by 
these bodies has no photographic power, the absorbed chemical rays being 
degraded to purely luminous ones. It is further stated that if a piece of 
burning magnesium wire is brought near to the sides of a white glass cylinder, 
filled with equal parts of hydrogen and chlorine gases, drops of hydrochloric 
acid will be seen to condense on the portion of the cylinder nearest the wire. 
If now a second piece of the wire is burnt on the opposite side of the glass, 
an explosion takes place almost instantaneously. 
Monthly Perturbations of Temperature. — A paper was read before' the 
Academy, on the 28th of August, by M. St. Claire Deville, having the fol- 
lowing title — “ On the Periodic Perturbations of Temperature in the months 
of February, May, August, and November.” It may be remembered that 
M. Deville made a series of observations on this subject in May last. He 
now communicates the results of similar observations made by him during 
the month of August. He gives a table containing the maximum and mini- 
mum of the thermometer, exposed and shaded, the quantity of aqueous 
vapour, the amount of ozone, and the barometric pressure during the “ critical 
periods ” of the month of August. This table shows a considerable increase 
of the mean temperature upon the 10th and 11th of that month. At the 
middle of the day, when the temperature was at its highest, the quantity of 
aqueous vapour decreased, but in the evening abundant rains raised its 
amount. From the 10th to the 13th the amount of ozone decreased, but 
augmented on the following days. The atmospheric pressure was high from 
