I 



Oct. 3, 1889] 



NATURE 



561 



into position of the metal spans, with estimates of weight, and 

 calculations of the resistances throughout the structure. The 

 metal required for this bridge would amount to a million tons, of 

 which about three quarters would be steel ; the cost is estimated 

 at ;,f35,ooo,ooo, and the period requisite to complete the work 

 ten years. This interesting pamphlet of nearly 100 pages will be 

 referred to on account of the careful manner in which the subject 

 has been brought forward, even should the building of the bridge 

 not take place, on account either of political objections or con- 

 structive difficulties. As stated in the paper itself, each pier com- 

 prises a small lighthouse, and as about 150 of these small light- 

 houses will have to be erected, an injury to any one of which 

 would close the bridge for a lengthy period, one thinks of the 

 Eddystone Lighthouse, built by Smeaton 100 years ago, which 

 has had to be replaced, not on account of any fault in its design 

 or construction, but because the sea had made inroads on its 

 foundation of rock. 



On Gaseous Fuel, by Sir Lowthian Bell. The author 

 assumes a certain quality of coal, and then compares the work 

 that can be performed with it according as it is used in the solid 

 state or in the condition of producer gas or in that of water gas. 

 Producer gas is that supplied to the Siemens regenerative gas 

 furnace ; the specimen of coal used for comparison is assumed 

 to consist of 70 per cent, fixed carbon, 16 coal gas, and 14 

 ash, oxygen and nitrogen, and the producer gas obtained from it 

 of 16 parts of coal gas, 163-3 of carbonic oxide, and 222 of 

 nitrogen, the producer gas being supplied cold at the foot of the 

 regenerators ; the calorific value of the coal is 7200 calories. 100 

 parts of this coal are equal to 720,000 calories, and by the com- 

 bustion of the producer gas 551,920 calories are produced, 

 showing a loss ot i68,c8o, equal to 23-3 per cent. The method 

 of manufacture of water gas is next explained. The fuel recom- 

 mended to be employed is coke, which is placed in a cylinder 

 of iron lined with fire-brick ; the coke is rendered incandescent 

 by an air blast. When in this state the blast is stopped, and a 

 jet of steam passed through it. The steam is decomposed ; its 

 oxygen burns the carbon into carbonic oxide, setting free the 

 hydrogen, the mixture constituting so-called water gas, compris- 

 ing equal volumes of carbonic oxide and hydrogen. The change 

 in producing water gas is expressed chemically by HgO -f- C = 

 H2 -V CO, and the heat required to tear hydrogen away from its 

 associated oxygen is not less than that evolved when the two 

 gases imite, or 2 x 34,200 - 68,400 calories. The weight of 

 •the combining equivalent of carbon required to effect the change 

 is twelve times that of the two units of hydrogen, and the heat 

 generated by this quantity of carbon being burnt to carbonic 

 oxide is 12 x 2400 = 28,80c, so that something over 14^ units 

 weight of carbon will be required to generate a unit weight of 

 hydrogen. But as only 6 units of carbon are being burnt per 

 unit of hydrogen, the incandescent carbon is soon cooled down 

 below the temperature of decomposition. When this point is 

 arrived at, the steam is shut off, and the blast is again turned on. 

 Using the data given in the water gas publications, water gas 

 produces per 100 parts of carbon 682,520 calories out of a 

 possible total of 800,000, there being a loss of 14-68 per cent, ; 

 as the coke used is produced from coal, the actual loss rises to 

 37 per cent. The author sums up as follows : — 



(l) Coal as burnt in an ordinary furnace- 



Calories. 

 = 720,000 



100 parts, yielding 7200 calories per unit 



Chimney gases, estimated after making the neces- 

 sary allowance for oxygen in the coals, 1 129 units 

 X427°C. X -24 specific heat = 115,700 



the loss in this case by chimney gases being equal to 16-07 per 

 cent. 



(2) Producer gas from same coal, as used in the Siemens 

 furnaces, without the addition of steam — 



Calories, 



70of carbon or 133-33 of CO x 2400 = 391,992 



l6 of coal gas x 10,000 = 160,000 



Sensible heat transmitted to furnace 62,411 



614,403 



Heat in chimney gases, 1 129 x 377° C. x -24 specific 

 heat 



Loss of chimney equal to 16-61 per cent. 



(3) Water gas and its accompanying producer gas — 



Water gas, i7°-5 C. = 4083 CO x 2400 = 



Hydrogen from steam, 2*926 x 29,400 = 



Producer gas, 52° 5 C, = 122-5 CO x 2400. 

 Coal gas, 16 X io,coo 



Calories. 

 = 97.99^ 

 = 86,024 



184,016- 



= 294,000 

 = 160,000 



... = 102,151 



Sum of heating-power of water gas and producer gas... 638,oi6' 

 Heat in a chimney gas assumed at same temperature as 



ordinary producer gas — 

 7797 X 377° ^ "24 sp. heat — 70,547 calories = 11-05 percent. 



These figures intimate that each 100 units of the three kinds 

 of fuel burnt there is afforded by: coal, 8-^-93 ; producer gas, 

 71-14 ; water gas and its producer gas, 78 80. 



To these figures of Sir Lowthian Bell the supporters of 

 gaseous fuel will object that, if with the use of gaseous fuel 

 there are 1 1 29 units of waste gases passing up the chimney, with 

 solid fuel there must be considerably more ; whilst the em- 

 ployers of the regenerative gas-furnace, whilst accepting 377° C. 

 as the temperature of their chimneys, will not allow the same 

 for water gas, where regenerators are not used. 



Another interesting paper presented to the meeting was one 

 by Mr. W. C. Fish, on the Thomson electric welding process. 

 The rationale of the process may be thus shortly described. If 

 an inclosed circuit of inappreciable resistance be completed by 

 the insertion and abutment of short lengths of the pieces to be 

 welded, the passage of an electric current through the circuit 

 will produce a transformation of electric into heat energy, and 

 the production of this heat will take place almost entirely at the 

 point of abutment of the metal pieces where the cross-section of 

 the conductor is virtually of least area, and the resistance is 

 proportionately great. If the current is of sufficient strength, a 

 welding beat is produced at the point of abutment, and, with 

 the aid of suitable pressure forcing together the heated extremi- 

 ties of the pieces, a weld is made. Various applications are 

 given in the paper, the employment of an alternating current 

 dynamo and a transformer being found the most effective method 

 of working. 



Mr. Alexander Siemens, in the discussion of this paper, 

 said he was able to confirm the general results given, for ia 

 making one of the Atlantic cables twelve years ago, it was found 

 that welding could be done more quickly by electricity than by 

 ordinary means. An electrical machine was placed alongside of 

 the cable machine, and they made all the joints for the sheathing 

 of the wire by electricity. They would find that the subject had 

 ben mentioned by Sir William Siemens in his address to the 

 Mechanical Section of the British Association at Newcastle in 

 1877. 



Papers were also presented to the meeting on the Robert- 

 Bessemer steel process, by Mr. F. L. Garrison, of Philadelphia; on 

 alloys of iron and silicon, by Mr. R. A. Hadfield, of Sheffield, both 

 being papers of a technical character. A new form of Siemens 

 furnace, arranged to recover waste gases as well as waste heat, 

 was described by Mr. John Head, and M. P. Pouff, of 

 Nevers. In this furnace, instead of two air and two gas re- 

 generators being employed, only a pair of air regenerators are 

 used, the gas being supplied hot to the furnace. Instead of the 

 whole of the products of combustion being passed through the 

 regenerators, a portion is directed through a regenerator to the 

 chimney, and the remainder through a converter producer, there 

 to be reconverted into combustible gases, and to do the work of 

 distilling hydrocarbons from the coal ; in fact, the gas producer 

 or converter in this furnace absorbs or utilizes the heat formerly 

 deposited in the gas regenerators, and in doing this transforms 

 spent gases into combustible gases. It had to be ascertained 

 ■whether the products of combustion from the heating chamber 

 would contain a sufficient amount of heat to insure their conver- 

 sion into combustible gases ; this has been found to be the case 

 in practice with furnaces working for the past six months. 

 Assuming that the producer contains only coke in the incandescent 

 state, this coke if fed with oxygen will produce carbonic acid in 

 the lower, and will be converted into carbonic oxide in the upper 

 zone of the producer ; if fed with hot carbonic acid instead of 

 oxygen, one-half the fuel, comprising the lower zone, may be 

 dispensed with, and an economy in weight of fuel to the same 

 extent realized. In actual practice finished rolled iron has been 

 heated in this furnace with a consumption of fuel as low as 2 

 cwt, per ton of iron. 



