230 Progress of Invention. 



sulphur or other mischievous ingredient. The apparatus required 

 for its production is of the very simplest kind, consisting merely of 

 a furnace, a still head, and a contrivance which serves both to wash 

 and purify the gas, and to retain it until required for use. It is 

 evolved at a temperature very far below that required for the 

 destructive distillation of coal, resin, etc., and therefore the cost of 

 fuel is insignificant, and the wear and tear of the apparatus next to 

 nothing. A ton of the refuse matter yields about seventy cubic 

 metres of gas. 



Novel Application op Electricity. — It is undoubtedly a 

 matter of considerable importance in many harbours that it should 

 be known with certainty by those about to enter or leave, when 

 there is a sufficient depth of water for the purpose. M. Emile 

 Duchemin has devised a very simple application of electricity, which 

 answers admirably for this purpose. He attaches to a small float 

 a plate of carbon and a plate of zinc, and connects these respectively 

 with the wires of an electric bell- ringing apparatus. Throwing the 

 float and battery into the sea will cause the bell to ring. "When 

 therefore they are suspended at any required height, within reach of 

 the tide, as soon as the water has risen sufficiently to set the small 

 battery in action, the bell will ring ; and thus the apparatus may, 

 at pleasure, be made to indicate any state of the tide. By using a 

 sufficiently large float and battery, it is evident that an electric 

 current will be generated sufficient to sound a bell of considerable 

 size, or, by means of Geissler's tube, to produce a light which will 

 be seen from a great distance. 



A simple Method or producing Ice on a Large Scale. — 

 Refrigeration is now used extensively for industrial and other pur- 

 poses. Solid matters dissolved in fluids are thoroughly separated 

 from them by freezing ; and the principle has been applied with 

 great success to the obtaining of the sugar from syrup, etc. A simple 

 and economic method of producing a freezing temperature is there- 

 fore of considerable importance. A new method of effecting this 

 has recently been tried in Paris, with very successful results. It 

 depends on the circulation of ether ; but unlike the other processes 

 in which this is used, it requires no pump. The amylic ether which 

 is employed is obtained and purified in the usual way. Its vapour 

 is transmitted at a pressure of from five to seven atmospheres into 

 a vessel, in which it becomes liquified. When a cock is opened for the 

 purpose, it passes from this vessel into spiral ducts which surround 

 the reservoir filled with the water, etc., which is to be frozen, and 

 immersed in a solution of salt, which is not frozen even by a very low 

 temperature. After having been vaporized in the spirals, the ether 

 vapour passes into three large cylinders containing sulphuric acid, 

 by which it is absorbed. A portion of the ether is always ready to 

 be driven from the saturated solution containing it, by means of 

 the heat which is supplied by superheated steam, into the vessel in 

 which it is again liquified, preparatory to its being again used for 

 the production of cold by evaporation. A machine calculated to 

 form in this way 200 kilogrammes of ice in an hour has been con- 

 structed for the separation of the salts contained in sea- water. 



