72 



NATURE 



[November 15, 1900 



shown in Fig. i. Although the trolley runs on a single rail, it 

 is prevented from falling over by the hook, and also by the fact 

 that the centre of gravity is immediately below the wheels. 

 The railway is a double track, one line for the up and the other 

 for the down trains. 



The curve of the track has an average radius of 90 metres ; at 

 Vohwinkel, however, there is a curve with a radius of 30 metres, 

 and in one place the radius of curvature is much less than this. 

 At each terminus of the line the track is built in the shape of a 

 large loop, so that the arriving carriages may pass round to the 

 departure platforms. The inclines are slight, the greatest 

 gradient being 45 in 100. 



The cars are propelled electrically, by current conveyed by 

 means of a sliding contact from generating stations to motors on 

 the trucks supporting the cars. Each truck has a motor of 30 

 horse-power, and works at a pressure of 600 volts. The cars 

 themselves are about thirty feet long and are of the corridor 

 pattern. There are two cars to a train, and each can carry fifty 

 passengers. No less than nineteen stations are provided in the 

 length of eight miles traversed by the line, and the trains 

 succeed one another every two or three minutes. 



as it did in 1870, and probably nearly four times as much as in 1850. 

 Durham and Yorkshire together are now yielding about as much 

 coal as the whole of the United Kingdom half a century ago. 



The unsatisfactory part of the particulars is the deficiency 

 of detail concerning our most important minerals, coal and iron 

 ore. County outputs are given, but no further descent into local 

 details is permissible, because the Coal Mines Regulation Act 

 prohibits the publication of the individual annual returns. While 

 a statement is made of the output of every little lead or tin 

 mine, it is impossible to state officially which of- our colliery 

 companies can be compared, for instance, with such great under- 

 takings as those at Anzin and Lens on the other side of the 

 Channel. Is it wise that no particulars should be kept of the 

 gradual depletion of our great national treasure? The total 

 yearly shrinkage is recorded, but no account is kept in our 

 official statistics of each individual vault which is being 

 drained of its riches. 



The Mineral Statistics Committee in 1894 recommended 

 the amendment of the Statute and the publication of the 

 output of individual collieries, but at present nothing has 

 been done. The anomaly involved in the present state 



Fig. I.— General view of a part of the Wupper Valley Railway at Klberfeld. The system of suspension of the trucks is shown in. the small figure. 



Each car is fitted with a Westinghouse pneumatic brake, a 

 hand brake and an electrical brake, so that it is well under con- 

 trol. The cost of the railway, comprising stations, permanent 

 way, and rolling stock, is stated to have been 56,000/. per mile. 

 The proprietor of the railway was Herr Eugene Langen, of 

 Cologne, who died before the line was completed. 



OUTPUT AND VALUE OF BRITISH 

 MINERALS.^ 



'T'HE most striking fact recorded in the mineral statistics for 



■*- 1899 is the enormous output of coal, viz., 220,094,781 tons, 



showing an increase of 18,040,265 tons compared with the 



previous year. This country is now producing twice as much coal 



1 Reprinted from a report by Prof. Le Neve Foster, F.R.S., on the output 

 id value of the minerals raised in the United Kingdom in 1899, the amount 



e of the metals produced, and the 



d by the Home Office. 



NO. 1620, VOL. 6^'] 



and 



aod value of the metals produced, and the exports and imports of minerals. 

 Published by the Home Office. 



of things is specially marked in the case of our iron ores. The 

 law prohibits the publication of the returns of stratified iron- 

 stone, but allows it in the case of unstratified iron ore. Conse- 

 quently, full details are given of the amount of ore produced by 

 each iron mine in Cumberland, whilst information concerning 

 the output of individual mines in the Cleveland district has to be 

 withheld from publication. 



Apart, however, from the question of the production of 

 individual mines, the total output for the year, amounting to 

 more than 220 million of tons and showing an increase of about 

 9 per cent, on the output for the previous year, points to the 

 urgency which the question of the exhaustion of the coal supply 

 is rapidly assuming. While it is impossible, in an annual 

 report on the mineral output, to undertake the task of estimating 

 the amount of coal still remaining in the British Isles, and of 

 attempting to arrive at any conclusion as to the time that may 

 elapse before its exhaustion begins to be felt, it may perhaps not 

 be out of place to call attention to the practical importance of 



