6o 



NATURE 



[_May 19, 1 88 J 



left, and the return journey was made by the way of the 

 Makalaka and West Matabele countries, and a hearty 

 welcome was given to the traveller on his arriving at Shos- 

 hong by the Mackenzies. While here the news arrived 

 that war had broken out in the Tranbvaal between the 

 Boers and Sekokuni. The journey to the Diamond Fields 

 was made by Limpopo, and shortly Kimberley was for the 

 fourth time reached. Settling at Bullfontein, the doctor 

 with indefatigable energy soon got into large practice, 

 and during two years, surrounded by the various animals 

 and birds he had collected in this journey, his esta- 

 blishment was quite a menagerie. One holiday he paid 

 a visit to the C'range Free State. When he viewed the 

 Rocky Caves used by the Bushmen, he was particularly 



attracted by the remarkable carvings on the rocks done 

 by the Bushmen to adorn their primitive abodes. A 

 sketch of some of these is represented in the adjoining 

 woodcut (Fig. 5). The rock is chiefly a sandstone, and 

 the drawings are frequently executed in coloured ochres. 

 After a considerable period spent at Bullfontein, at 

 Grahamstown, at Port Elizabeth, arid at Cape Town, he 

 embarked on board the Gcnnania for Europe in August, 

 1S79, bringing wiih him large ethnological and natural 

 history collections. While the author's travels have 

 added something to our previous knowledge of the geo- 

 graphy of the portions of Africa he traversed, his 

 account of them is really pleasant reading, and will be 

 found of special interest to the naturalist and sportsman. 



ELECTRIC LIGHTING ' 

 III. 

 T^ECIDEDLY the most successful application of the 

 -'-^ electric light in London is at the Cannon Street 

 station of the South Eastern Railway. The Charing 

 Cross station of that Company has been lit up by the 

 Brush system, and the Bricklayers' Arms goods-yards 

 and sheds by Mr. Crompton's system, so that the South 

 Eastern Railway officials have an admirable competitive 

 trial proceeding within easy reach of inspection. The 

 Cannon Street station is lit up by the British Electric 

 Light Company with Gramme machines and Brockie 

 lamps. 



The engine — one of Marshall's semi-portable type — is 

 of 14 horse-power nominal, and has a double cylinder on 

 a locomotive boiler. The power is transferred by counter- 

 shafting to the dynamo-machines by a system specially 

 designed for the purpose, which is shown in the follow- 

 ing sketch (Fig. 2). Large heavy fly-wheel pulleys give 

 a second motion to the fly-wheel, which secures great 



-J 



steadiness — an essential feature of electric lighting. The 

 engine is controlled by Hartnell's automatic governor, 

 which regulates the e.xpansion-gear of the engine and 

 secures great uniformity of action. 



The dynamo-machines are of a new class of Gramme, 

 of high electromotive force, and they generate currents 

 powerful enough to work five lamps. The current pro- 

 duced is of 26 vebers strength, and works a circuit of about 

 8 ohms resistance, thus giving an electromotive force of 

 20S volts. There are two machines at work, working ten 

 lamps- eight being inside the station and two outside. 

 The dynamos are fed by smaller Grammes, as shown in 

 Fig. 2. 



The lamps are Brockie's, the mechanism of which is 

 extremely simple, consisting only of one magnet with a 

 clutch, which, by means of a branch circuit, periodically 

 interrupted by the commutator, readjusts the arc by 

 letting the clutch fall, which releases the carbons and 

 brings them momentarily together, and then picks them 

 up again \ ery smartly, so as to separate them the re- 

 quired distance. This gives the lamp a blinking habit, 



-■>*S*JS%5^: 



which at first is peculiar, but which one soon gets 

 accustomed to and ignores. The diagram (Fig. 3; 

 clearly illustrates how this is done. The magnets 

 are fixed on shunts, two lamps being on two shunts and 

 one lamp on the other. The shunts are of smaller wire 

 than that of the main circuit, but they do not interfere 

 with the main current, which passes through the carbons 

 — in fact the shunts reduce the total resistance of the 

 circuit. The lamps burn for four and a half hour?, but it 

 is intended to introduce a double set of carbons, which 

 will of course duplicate this time. 



Mr. Brockie has introduced quite a new principle into 

 electric lighting, and certainly, to judge from the effect at 

 Cannon Street, his success is unqualified. It remains to 

 be seen how far this success is repeated at the General 

 Post Office, at Victoria Street, Manchester, at Prince's 

 Dock, Liverpool, and in the town of Liverpool itself. 

 We certainly would hke to see a good west-end street, 

 say Piccadilly, Regent Street, or the Haymarket, lit up by 

 this system. 



Another system, not yet extensively employed, is Joel's 



*S>'«l*:«3F>l«S!.a^5**?''i9!!B**W=' 



improved incandescent electric lamp. In the latter part 

 of 1878 considerable interest was excited in both scientific 

 and commercial circles by the announcement that M. 

 Werdermann had succeeded in the so-called division of 

 the electric light by an invention based on the incandescent 

 principle. His system was exhibited on an experimental 

 scale only for some time, and then suddenly disappeared 

 from public notice. 



This incandescent principle has recently been revived, 

 with many and ingenious improvements in the mechanism 

 of the lamp, by Mr. Joel. .An illustration of the hanging 

 lamp is shown in Fig. 4. The light is reproduced, as was 

 the case in M. Werdermann's system, by the heating to in- 

 candescence of the end of a small rod or pencil of carbon 

 forming one electrode, which protrudes through a pair of 

 ' contact jaws and abuts upon a fixed cylinder of copper 

 forming the other electrode. The carbon pencil consumes 

 I at the rate of 2j to 3 inches per hour for lights of 100 

 j candle-power and upwards, and is fed forward according 

 to the consumption. The length of carbon in circuit 

 between the contact jaws and the fixed electrode is about 

 three-quarters of an inch, and this, by the passage of the 



