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KNOWLEDGE .S; SCIENTIFIC NEWS. 



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practically proportional to the speed, so that the intensity 

 of the current may be regarded as constant. This is 

 further demonstrated by the author's measurements. 



The current from the dynamo is used to charge an accu- 

 mulator battery represented diagramniatically in P'ig. i. 

 The cut out switch F is closed, pro\ided the current in- 

 tensity be not inferior to its normal constant value. The 

 dynamo D therefore works at a variable speed. In the 

 case of the wind being so strong as to absorb part of the 

 energy by the friction of the belt, the system will work in 

 the following way : .\ssummg the accumulator battery to 

 be nearly discharged and the crank of the cell controller 

 to be adjusted for the total charge of the battery, llie 

 dynamo will run at a speed so high as to be quite suffi- 

 cient to charge the battery with the normal current of a 

 dynamo (e.g. 50 amp.). As the charge increases, the 

 dynamo will automatically increase its speed and load 

 so as to make the charging current constant. The cell- 

 controller will have to be resorted to in charging in 

 exceptional cases only — if, for instance, the charging 

 and discharge of the battery takes place at the same 

 time. 



The electrical regulating device is situated in the inter- 

 rupter S, being mainly an ordinary minimum current 

 interrupter, disconnecting the dynamo as soon as the 

 current decreases below the normal number of amperes. 

 This arrangement is necessary to prevent the accumu- 

 lator battery from being discharged through the dynamo 

 when the strength of the wind is small. The interrupter, 

 however, will automatically insert the current as soon as 

 the wind again assumes a greater strength. To attain 

 this result, the current interrupter is provided with a ten- 

 sion regulator, inserting the current as soon as the speed 

 of the dynamo has sufficiently increased. In the case of 

 variable strengths of the wind, the plant may thus accumu- 

 late any amount of wind available, the interrupter open- 

 ing and closing the connections continually. On the 

 switchboard there are in addition two ammeters and one 

 voltmeter. 



A small electricity works arranged in accordance with 

 the foregoing principle has, as above mentioned, been in 

 operation in Askov since the beginning of last autumn, 

 supplying the inhabitants of the neighbouring commu- 

 nities with electric current. The constant normal current 

 supplied by this installation is 60 amps, at tension of 220 

 volts. As a reserve, however, in cases of several days' 

 calm weather, a petroleum motor had to be installed. 

 The plant has so far given every satisfaction, requiring no 

 superintendence worth speaking of. The man in charge 

 of the machine was away fer|whole days, so that there 

 was no supervision except "Jin^^the morning and the 



The W'ork.s at A.skov. 



evening. The capacity of the accumulator battery is 

 sufficient to supply the maximum amount of energy 

 required during 48 hours. As regards the economical 

 side of the question : The (irst cost at .'VsK-on- has been 

 about 16,000 Kr. (a Kroner is about is. id.), out of which 

 3000 Kr. are set aside for the cost of pstroleum nioliir. 

 The electric current is supplied to consumers at the 

 same price as in Copenhagen. The receipts for energy 

 sold work out at about 2800 Kr., and the expenses al 

 about 800 Kr. per year. There will thus remain 

 2000 Kr. for the amortisation of the plant, which is more 

 than sufficient with a capita! of i6,ooo Kr. The price of 

 energy could therefore be further diminished. In ihe case 

 ofsniall electricity works intended for the use of a limited 

 number of houses, the petroleum motor may be replaced 

 by a horse-driven contrivance. Moreover, in the case of 

 the proprietor of the works being his own consumer, the 

 consumption of current may be regulated according to 

 the actual intensity of the wind; in the case of calm 

 weather, there will for instance have to be no thrashing 

 done, cVc. The first cost will thus be considcraoly 

 diminished; according to I'ref. Latour's calculation, a 

 plant suitable for a farm would be installed at a cost of 

 3000 to 4000 Kr. 



The Canals on Mars. 



Ix a communication to the Royal Astronomical Society 

 on June 12, 1903, as reported in the Olwrvaloi'v for July, 

 Mr. Maunder called in question the objective reality of 

 the canals on Mars, explaining them away as psycho- 

 logical phenomena " due to the integration by the eye 

 of markings far too small to be observed by the observer." 

 He based his argument on the fact that copies of draw- 

 ings of Mars without the canals, made by beys of from 

 12 to 15 years of age placed at \'arieus distances from the 

 drawings, contained lines resembling canals amounting 

 to five canals per head as a maximum at a distance of 

 25 feet, the diameter of the disk being about 6 inches. 

 Unfortunately, the report gives us no information as to 

 the closeness of coincidence of the lines with canals that 

 have been actually observed, nor even as to the agree- 

 ment between the lines drawn by different boys. It is 

 difficult to see hew the drawings to be copied could have 

 contained actual Martian markings that were " far too 

 small to be observed," whose integration produced lines 

 in the positions in which canals have been observed ; 

 but if the drawings were not sufficiently accurate to show 

 such markings, the lines must have been produced by 

 markings peculiar to the several drawings, whose resem- 

 blance to anything on the planet is highly improbable. 

 In drawing inferences from a comparison of artificial 

 experiments with natural phenomena, it is certainly 

 essential to the value of the results that the artificial and 

 natural phenomena shall be substantially identical, and 

 that the observations shall be made under practically the 

 same conditions in both cases. On a later occasion, Mr. 

 Maunder himself strenuously insists upon the necessity 

 for a very close resemblance between the phenomena and 

 between the conditions of observation in such cases. In 

 criticising Mr. Lowell's application of the results of his 

 experiments on the " visibility of fine lines " (the Oliscrva- 

 tory for September, 1903), Mr. Maunder says "there is 

 actually no resemblance between the case of observing a 

 wire in space and that of observing a line drawn on a 

 surface " ; nevertheless, he seems to find a sufficiently 

 close resemblance between the observation of a flat 

 picture (inaccurate, at best) with the naked eye in a 



