262 Chronicles of Science. | April, 
belts of Jupiter is much more perceptible with 6-inch apertures 
than with apertures of 12 inches: also a small star in the cluster 
in Perseus appears of an indigo-blue with 83 inches, Prussian-blue 
with 104 inches, and royal-blue with 12} inches of aperture. 
From this it follows that colours estimated by comparison with 
Admiral Smyth’s chromatic scale, in which each colour is repre- 
sented of four degrees of intensity, can possess no relative value 
unless taken with the same aperture. 
The spectroscope has received from Professor Osborn, of La- 
fayette College, U.S., improvements which have rendered it ap- 
plicable to a variety of practical purposes, particularly in metallurgy. 
By means of the instrument thus modified it is possible to detect 
in a room many hundreds of yards from a furnace, the sodium in 
the coal, or decomposed fire-brick, also any lime, potash, &c., pro- 
ceeding from the furnace-mouth. Professor Osborn is hopeful of 
peru uses being found for the form of spectroscope he has 
evised. 
Dr. Emerson Reynolds, at a meeting of the Dublin Chemical 
and Philosophical Club, read a paper “On the Action of Ozone on 
Sensitive Photographic Plates.” He had found in experimenting 
upon this subject that the latent or undeveloped image submitted 
to the action of ozone was completely obliterated: a second image 
might be taken on the plate. Dr. Reynolds remarked that, this 
fact was at variance with what might be called the mechanical 
theory of photographic images, and proved conclusively that the 
production of an image was due to a chemical change in the sen- 
sitive fim. He thought that the disputes with regard to the time 
dry plates might remain sensitive, arose m some degree from the 
variable amounts of ozone present in the atmosphere. The ozone 
used in the experiments was in some cases obtained by passing 
atmospheric air over phosphorus, in others by the aid of electricity. 
A new photometer has been devised by Mr. C. H. Bennington, 
M.A., and described by him in the ‘ Philosophical Magazine.’ 
In a paper “On Phosphorescent Light,” Dr. Kindt mentions 
that a piece of chlorophane, which heated im a tube gives a green light 
visible in daylight, viewed through a spectrum apparatus in the 
dark shows homogeneous green only. Phosphorite of Estremadura 
shows green, yellow, and red. A green fluorspar, from the Breisgau, 
shows two dark lines in the green, one of which is near the orange 
red. The dark lines are as powerful as in solutions of didymium. 
Two other bright green fluorspars give rise to the same bands. 
Mr. William Huggins, F.R.S., has described to the Royal 
