April 22, 1909J 



NA rURE 



235 





gases, &c. ; the steam generated represents 8g6 units, and 

 of these i!2 are lost by condensation, &c. The steam 

 supplied to the engine represents 7S4 units, and of these 

 bb7 are lost in the exhaust, so that only 117 are converted 

 into indicated work, and from this 17 are deducted for 

 friction. In Fig. 4 525 heat units are absorbed in the pro- 

 ducer, and of these 105 are taken as lost in ashes, radia- 

 tion, cooling of gas, &c. The gas supplied to the engine 

 represents 420 units, and, as in Fig. 3, 117 units are con- 

 verted into indicated work, and of these 17 are deducted 

 for friction. In Fig. 5 16S0 heat units are absorbed in 

 the boiler, and of these 420 are lost in ashes, radiation, 

 &c. ; the steam generated represents 1260 units, and of 

 these 84 are lost by condensation, &c. The steam supplied 

 to the engine represents 1176 units, and of these no less 

 than io5g are lost in the exhaust. In Fig. 6 494 heat 

 units are absorbed 

 in the producer, and 

 of these 74 are taken 

 as lost in ashes, 

 radiation, cooling of 

 gas, &c. The gas 

 supplied to the 

 engine represents 420 

 units, and the remain- 

 ing losses are similar 

 to those in Fig. 4. 



On these bases the 

 general result is that 

 for the 2SO-B.H.P. 

 size, in order to 

 obtain too heat units 



0. cq in useful work with 



I io steam power there 



_ ; I must be 1120 heat 



units in the fuel con- 

 sumed in the boiler ; 

 whereas with gas 

 power there need 

 only be 525 units in 

 the fuel consumed. 

 This shows a saving 

 of S3 PS"" cent, in 

 the weight of fuel 

 in favour of the gas 

 plant. The result is 

 still more striking in 

 the case of the 40- 

 B.H.P. size, as there 

 must be 1680 units 

 in the fuel consumed 

 j_.^ for steam power 



■5 g ^ compared with 4q4 

 '^ a-S for gas power. This 

 is a saving of 70 per 

 cent, in favour of 

 the gas plant. These 

 figures do not in- 

 clude any allowance 

 for stand-by losses, 

 which would be con- 

 siderably less for gas 

 than for sti'am 

 power. 

 After considering the two types of plant, I think our 

 general conclusions may be as follows : — A suction plant has 

 certain practical advantages — it costs less and occupies a 

 smaller ground-space ; but the gas made in it is not so 

 strong as in the older form of pressure plant, and in the 

 case of large engines this advantage may be important, as 

 it affects the maximum power of the engine. The fuel 

 consumption per H. P. -hour and the labour required are 

 about the same in both types of plant, provided the steam 

 required is raised without an independent boiler. The con- 

 sumption of water is the same in both types. Where 

 there are several engines to serve, a pressure plant is 

 better, as all can be served with one main from the gas- 

 holder, with a branch to each engine. This simplifies the 

 piping and reduces its cost considerably ; it also facilitates 

 the starting of the engines. It seems to me that e.ich 

 plant has its own province, and that in some cases the 



NO. 2060, VOL. 80] 





gifl 



5S 



55 Si 



^5 





Fig2_ BbAl Fig a. Li93^ 



-250 K.H.I!, sle: 

 -230 U.K. P. gas. 

 -40 K.H.I' ^.ual 

 -40 H.H.P. gas. 



pressure type is better than the suction type ; in others 

 suction is better than pressure. 



Looking at the matter broadly, one cannot but be struck 

 with the enormous development in gas power which has 

 taken place during the last ten, and especially during the 

 last five, years. Small steam engines are being rapidly 

 superseded, and in several cases the makers of steam 

 engines are now making gas engines. At first only small 

 gas engines were supposed to be within the range of prac- 

 tical politics, but those days are over, and there are many 

 gas engines developing more than 1000 H.P. each which 

 are working satisfactorily. Gas power has come to stay, 

 and now has a recognised position among engineers. 



J. Emerson Dowson. 



O' 



TRANSATLANTIC WIRELESS TELEGRAPHY."- 

 N previous occasions I have had the honour of 

 describing before this institution some of the stages 

 through which the application of electric waves to tele- 

 graphy through space has passed. This evening I propose 

 to confine myself chiefly to describing the results and 

 observations recorded during the numerous tests and 

 experiments which my collaborators and I have been carry- 

 ing out with the object of proving that wireless telegraphy 

 across the Atlantic was possible, not merely as an experi- 

 mental feat, but as a new and practical means for com- 

 mercial communication (Journ. Inst. Elec. Eng., xxviii., 

 iSgg, p. 20 1). 



In March, 1899, communication was established by means 

 of my svstcm of wireless telegraphy across the Channel 

 between 'England and France (see Fig. i), and the Times 



FIG.l 



of March 29 of that year published the first Press telegram 

 ever transmitted to England from abroad by means of 

 electric-wave telegraphy. 



.•\t that time a considerable discussion took place -n the 

 Press as to whether or not wireless telegraphy would be 

 practicable for much longer distances than those then 

 covered, and a general opinion prevailed that the curvature 

 of the earth would be an insurmountable obstacle to long- 

 'distance transmissions, in the same way as it was, and 

 is an obstacle to signalling over considerable distances by 

 means of optical signals such as flashlights, the heliograph, 

 or the semaphore. 



Other difticultjes were anticipated as to the possibility of 

 being able practically to employ and control a transmitter 

 capable of radiating an amount of electrical energy large 

 enough to actuate a receiver at really great distances, and, 



I From a discourse delivered at the Royal Institulionon Friday, March 13, 

 1908, by Commendatore G. Marconi. 



