SCIENTIFIC SUMMARY. 
441 
The improved Tuning-fork. — Mr. H. Jones has patented a new form of 
tuning-fork^ of wliicli tke following account is given in tlie specification. 
The inventor uses a sheath or case, into which he fits a tuning-fork so that 
the forked ends remain free to vibrate therein, and in such ends openings 
can be made in the above-named case or sheath, a striker being fitted therein, 
usually radiated with three, four, or more radii, so that two remain within, 
and one, two, or more, protrude beyond the case or sheath, which striker, 
upon being pressed by the thumb or finger, presses the end of the tuning- 
fork, which, when suddenly relieved, emits the musical sound. 
The Spectrum of the Aurora Borealis. — According to the researches of 
Herr J. A. Angstrom, the light exhibited by the aurora is almost always 
monochromatic, and shows a single bright line to the left of well-known 
lines of the calcium group. 
How to deter^nine Bhosphorescence experimentally. — An instrument has 
recently been devised by M. Laborde, and has been named the phosphoro- 
scope. It is thus described in Les Mondes : It is based upon the same 
principle as that of M. Becquerel ; its essential parts are a Ruhmkorff induc- 
tion apparatus, the spark of which throws light on the phosphorescent object, 
and of a sliding frame, one of the ends of which hides the obj ect during the 
brief moment it is illuminated by the electric spark. This sliding frame is 
40 centimetres in length by 10 centimetres in breadth j it is fixed at its 
centre on an axis, which may be made to move rapidly by means of a pedal. 
The arrangement of this apparatus is such as to render it serviceable for 
studying the phosphorescence excited by a blow, as well as by friction. 
The phenomena of phosphorescence of substances which, like nitrate of 
uranium, is only of very short duration, can be observed by means of 
this instrument ecLually well as the long- continued and strong phos- 
phorescence induced by friction in pieces of porcelain or glass. 
Hoes Sunlight extinguish a Fire ? — Mr. Tomlinson thinks he has decided 
this question, and in a paper read in the Chemical Section of the British 
Association he expresses the results at which he has arrived. Experiments 
on the subject are not easily made, in consequence of the many disturbing 
causes ; but from some experiments found in an old volume of the Annals 
of Philosophy, made upon coloured tapers, the conclusion arrived at was that 
the solar rays, in proportion to their intensity, have the power of retarding 
to a considerable extent the process of combustion, but this conclusion is 
open to objection. From a series of experiments upon candles of different 
sizes and weights, in dark chambers and day and sunlight, Mr. Tomlinson 
found that the increase of temperature led to increased consumption of 
material, and vice versa, and the whole result may be stated, that in any 
case the difference is so small that it may be referred to accidental circum- 
stances, such as temperature and material — the final conclusion being 
that the direct light of the sun, or the diffused light of day, has no 
action on the rate of burning, or in retarding the combustion of an ordi- 
nary candle. 
Condensing Magnetism. — Although this expression is open to objection 
it explains what is meant by the phenomenon. In a paper lately presented 
to the French Academy by M. Jamin, this physicist showed that magnetic 
power may, like electricity, be accumulated. Having, for some special 
