SCIENTIFIC SUMMARY. 
217 
PHYSICS. 
The Spectrum of Uranus. — In the u Oomptes Rendus ” (February 26, 
1872) Father Secchi has a paper which contains the following results. He 
says that during one of the line evenings of February he has been examining 
anew the spectrum of Uranus. He states that he has found the three 
bands that he formerly observed : one in the red, one in the yellow, and the 
third in the blue ; this latter coincides really with the line as pointed out by 
Mr. Huggins and M. Vogel, contrary to that which he believed he saw at 
the period of the discovery of this curious spectrum. But he says that the 
band of the red requires, in order to be visible, an atmosphere perfectly 
clear. He is not surprised therefore that it has not been observed. 
An Apparatus for Studying Vibration. — We hear of an ingenious con- 
trivance for the above, which has been invented by an American gentleman. 
A disk of white cardboard, with apertures oblong in radial direction, is set on 
a spindle, so as to be rotated at any requisite speed. To examine, for in- 
stance, the flame of a gas light (in a glass tube, to prevent disturbance by 
air currents), place the disk in front of the light, so that the eye can see the 
light through each slit as it comes to a vertical position. If the speed of 
the disk’s rotation is such that the interval of time between two slits pass- 
ing the eye is just equal to the period of a vibration of the flame, the flame 
appears to be motionless ; but if the velocity be reduced, the flame is seen 
to go slowly through its changes of form. If the interval be equal to, or one- 
half of, or one-third of, the period of the vibration of the light, the illusory 
appearance of a disk having as many as, or twice, or three times the number of 
slits really in the disk is seen. This phantom disk will appear to be motion- 
less when the periods coincide ; but when otherwise, it revolves in one 
direction or the other. It is obvious that the vibrations of the flame can be 
easily counted by this means. The inventor, Mr. Charles J. Watson, 
counted with a sixteen-inch tube, 453 vibrations of the flame per second. 
By this instrument, the undulation of the vibrations of a wire can be seen 
to travel up and down the wire; and if watched by both eyes through the 
slits, the spiral course of the undulations can be observed. 
A New Source of Electricity has been discovered by Dr. James St.-Clair 
Gray, and is thus reported. There was prepared a cell containing a 
solution of caustic-potash, in which phosphorus and sulphur, both in sticks, 
were placed. Within half an hour the phosphorus was reduced to an 
oily mass, perfectly mobile, occupying the lower part of the cell; the 
sulphur was not at first affected. The temperature at first rose consider- 
ably — about 20° — but this soon passed off, and the solution returned to 
the temperature of the surrounding medium, varying from 56° to 60° F. 
During the first six days there was a constant development in small quantity 
of phosphuretted hydrogen in the spontaneously inflammable form; but 
after that time, although phosphuretted hydrogen still continued ' to bo 
evolved, it no longer ignited spontaneously, this being probably due to the 
simultaneous development of sulphuretted hydrogen, which began to be 
exhaled in appreciable quantity about this time. At first the sulphur was 
little affected, but at the end of ten days it’ was found that at the point of 
junction of the phosphorus therewith, there had occurred considerable loss of 
