1874.] Technology. 419 
importance of this for scientific discoveries and industrial purposes is evident. 
For the purposes of war, also, must such a small and comparatively cheap 
submarine vessel place a peculiar, nay a decisive, weight in the scale in the 
question of our modern ironclads. Freezing machines working by evaporation of 
carboleum produce ice at a much less cost than any existing freezing apparatus. 
Regarding this general usefulness of carbonic acid, it is important to call 
attention to the faé& that an inexhaustible store of carboleum. is at our dis- 
position in common chalk, for this mineral contains carbonic acid to the 
amount of half its weight; it can therefore produce twice its volume of 
carboleum. 
Evectricity.—M. Clamond has been improving his thermo-eleétric pile. 
He found in it a considerable increase of resistance, and this was 
due to two causes—(r1) Oxidation of the contracts of the polar plates 
with the crystallised bar under the influence of heat ; and (2) split- 
ting of the bar and separation of its different parts in planes perpen- 
dicular to its length. In making his couple he uses an alloy of zinc 
and antimony, and plates of iron as armatures. The bars are collected in 
crowns of ten bars each, superposed and separated by washers of amianthus, 
and coupled for tension. The whole forms a cylinder, the interior of which is 
luted with amianthus, and heated by means of a pipe of refractory earth 
pierced with holes. The gas mixed with air burns in the annular space 
between the tube and the bars. The entire surface of the crowns of the pile 
is 35 Square decimetres. The consumption of gas is controlled by M. Girond’s 
regulator. Thus arranged, the pile will work whole months without requiring 
attention, giving a current absolutely constant. A model exhibited consumed 
170 litres, that is, about 5 centimes of gas in the hour, and deposited 20 grms. 
of copper, which makes the expense of gas per kilogrm. of copper deposited 
2 francs 50cents. M. Clamond has made models of various size; the quantity 
of electricity increases proportionally to the size of the pieces. 
The lever of an electric automatic whistle for locomotives is wrought 
by an elefro-magnet. On passage of a current in a certain direction 
_ the magnet lets go the lever, and the whistle sounds. The apparatus 
is connected by insulating wires with a metallic brush projecting 
below the locomotive. At a short distance in front of the sight signal there 
is a metallic plate between the rails, which, when the signal is turned in the 
position for stoppage, is connected with a source of electricity. On passage 
of the brush over the plate the current flows and the whistle sounds. It con- 
tinues to do so till adjusted again by the engine-driver. The Chemin de Fer 
du Nord have used the system, which is the invention of MM. Lartigue and 
Forest, eight months, and with satisfactcry results. 
The following safety eleGric cable against fires is proposed by MM. Joly 
and Barbier:—Two wires, insulated from each other by gutta-percha, are 
corded together into a cable, and are connected at one end with a battery and 
electric bell. When fire breaks out in any part of the building through 
which the cable passes the gutta-percha is freed and the wires come in con- 
tact, thus closing the circuit and ringing the bell. The condition of the ap- 
paratus is tested by means of a peg commutator at the other end of the cable. 
TECHNOLOGY. 
A new use of glycerin is to prevent the formation of incrustation in steam- 
boilers. M. Asselin, of Paris, recommends the addition of glycerin in the 
proportion of 1 kilo. for every 5000 to 8000 kilos. of fuel consumed, on account 
of its power of increasing the solubility of sulphate of lime, and causing the 
undissolved portion to be precipitated in a granular form, so as not to adhere 
to the metal. 
As a system of continuous alarum signals to prevent collisions, on railways 
or at sea, in foggy weather, M. de Mat proposes to compress air in a cylin- 
drical reservoir, from which a tubulure conveys it to three organ pipes (giving 
do, mi, sol), whick can be sounded separately or together. In fog the do is 
sounded, and whenever an engine-driver hears it in an advancing train he 
sounds his mi, the other driver then sounds his mi if he is on the right line, 
then both sound sol. 
