680 
POPULAR SCIENCE REVIEW. 
How to Mahe an Intermittent Fountain. — M. I’Abbe Laborde, writing to 
Les Mondes, describes a simple apparatus for producing an intermittent 
fountain. It consists of an inverted flask fitted with a cork, through which 
pass two tubes of unequal length. The longer reaches nearly to the bottom 
of the flask, and outside has a length of some twenty inches. The shorter 
tube merely pierces the cork, and does not extend to any length inside, and 
outside it ends immediately in a jet, which can be curved round. The flask 
is filled with water, fitted with the two tubes, and then, with the finger on 
the shorter tube, is inverted, plunging the end of the longer tube in a vessel 
of water. The instrument may now be fixed in this position, as an inter- 
mittent jet of water begins to flow at once, continuing imtil the flask is 
empty. The column of water in the longer tube will be seen to be alter- 
nately rising and falling, from which phenomena an explanation has been 
given of the cause of the intermittent flow. 
A Powerful Thermo-Electric Battery. — At a meeting of the Koyal Institu- 
tion, held some time ago, Mr. Ladd exhibited in the library a powerful 
thermo-electric battery, made in the manner invented by Marcus, of Vienna. 
Although the instrument consisted of only ten pairs, and the means of 
heating it by a row of gas jets had been hastily devised, yet on making and 
breaking the circuit a spark was readily obtained. The current from this 
thermo-electric battery was sent round an electro-magnet, and lifted a very 
considerable weight. 
A Novel Method of Telegraphy. — M. Eugene Godard, the imperial aeronaut, 
has made some very interesting experiments on the subject of a new method of 
telegraphing. By the aid of a single luminous point M. Godard sends messages 
to any part of the visible horizon. The experiments were tried at the Obser- 
vatory and in the Kue de Puteaux. A lamp to which a reflector was fixed was 
placed m the third floor of a house in that street, while a similar lamp was 
burning on the terrace of the Observatory. Within three minutes M. Godard 
sent a message of twenty words to the Observatory. The system is extremely 
simple. By means of screens, which by concealing or allowing the light to 
escape, partial or total eclipses are produced. The screens are either of white 
or red glass. The colours emitted and the duration of that emission sufiice 
to form an alphabet analogous to that of words used by the usual electric 
telegraphs. The extreme simplicity of this method would be specially useful 
for signalling at sea in times of war. Two corps larmee could thus most 
easily communicate with each other. 
Lightning Conductors. — At one of the summer meetings of the Brussels 
Academy of Sciences, M. Melsens read a note “ On Lightning Conductors, 
and on some Experiments on the Induction Spark.” Instead of a solid 
rod, he proposes to use a bimdle of wires of small diameter ; the total area 
of cross section to be at least equal to that of an iron conductor ‘020 m. 
square, or ‘02 m. diameter. In the case of the Hotel de Ville he suggests 
that the conductor be composed of eight galvanized iron wires ’007 m. in 
diameter at least. The principal rods are to be led into a well, and are to be 
connected by numerous branches with the water and gas pipes of the 
building. 
Luminous Radiation at a Red Heat. — An essay on this subject appears in 
the Comptes Rendus for July 3rd. It is written by M. Desains. The author. 
