136 



NATURE 



\yune 8, 1876 



the wires of the revolving cylinder, the revolution of the 

 latter causes a powerful current to pass into the electro- 

 magnetic coils, this again inducing a still more powerful 

 current in the wires of the cylindrical armature. The iron 

 core of the cylindrical armature being very close to the 

 poles of the electro-magnets, becomes itself an intensely 

 powerful transverse magnet of opposite polarity to the 

 electro-magnet. The cylinder of wire thus revolves in a 

 very intense magnetic field. 



These electrical currents are collected on two metal 

 rollers or brushes, so that at two points diametrically 

 opposite the single sectors pass under the rollers or 

 brushes with elastic pressure giving up to them their elec- 

 trical charge. 



A slight increase of speed in the rotation of the wire 

 cylinder is followed by a considerable increase of current, 

 but as the current increases, so does the resistance to ro- 

 tation ; and this very rapidly. In addition to this heat is 

 developed to such an extent, that care must be taken not 

 to exceed a certain limit, otherwise, the insulation of the 

 coils would be destroyed. Were it not for this drawback 

 almost any amount of current might be produced with 

 suitable driving power. 



As the external resistance affects the strength of the 

 current the speed must be varied accordingly, being 

 greater as the external resistance is greater and vice versd. 

 With an electric lamp in a circuit of small resistance, if 

 the machine is intended to work continuously, the revolu- 

 tions of the wire cylinder per minute should not exceed 

 370 to 380. The temperature of the machine will then be 

 at a maximum in about three hours ; and during work will 

 remain constant. At this speed the driving power is about 

 eight indicated horse-power. While the intensity of the 

 light, unaided by reflector or lens, has been shown by 

 various photometers to be equal to 14,000 normal English 

 candles. A more intense electric light cannot be obtained 

 as any increase in the current splits up even the best 

 carbon. 



The conducting wires from the machine to the lamp 

 should be of copper, offering very little resistance and at 

 the same time possessing a high electrical conductivity. 

 If the lengths of the two wires do not together exceed 

 fifty-five yards, then a wire of 0-157 inches diameter, and 

 of high conductivity will suffice. For longer distances it 

 is advisable to use a strand of larger diameter. 



Increased speed will of course compensate for decrease 

 of current due to a too great external resistance, but this 

 can be done only at the expense of increased motive 

 power. 



The lamp used with the machine is regulated without 

 clockwork, as the employment of the latter has not only 

 been a source of numerous failures and difficulties, but is 

 liable to disarrangement upon the least rough usage. The 

 lamp of itself regulates the carbon points, keeping them 

 at a uniform distance, and thus a perfectly steady light is 

 produced. 



For concentration either a parabolic reflector or a 

 Fresnel dioptric lens may be used. 



For transportation the Dynamo-electric Light Appara- 

 tus is mounted on a waggon, with steam-engine, the whole 

 weighing 4,96olbs. The combination has proved very 

 serviceable on account of its lightness and compactness. 



THE ETHNOLOGY OF THE PAPUANS OF 

 MACLAY COAST, NEW GUINEA^ 



"liriTH regard to the villages and dwellings. So thickly 

 * • is the eoast of Astrolabe Gulf covered with vegetation 

 that no houses are visible to anyone on shipboard, the 

 only signs of habitation being perhaps columns of smoke. 

 If, however, more careful observation be made with a tele- 

 scope, separate groups of cocoa-nut palms will be noticed. 



' Continued from p. ic^ 



If a landing be effected near one such group, 2. pirogue, 

 or canoe, will probably be seen drawn up on the shore, or 

 else concealed in the jungle, and a path will be found 

 leading through the wood to an open clearing, where 

 stand huts overshadowed by bananas and cocoa-nut 

 palms. Viewed from the side, one such hut seems almost 

 wholly to consist of roof, as the side walls rise scarcely 

 half a yard above the ground. A semi-circular eave-like 

 projection frequently stands out over the doorway. Close 

 in the neighbourhood of nearly every hut there stands 

 upon four legs the barla, a kind of table or bench, which 

 serves as the eating and resting-place of the men. Upon 

 this, when the meal is ready, the host and his guests are 

 seated, so that they can take their meal without fear of 

 molestation from pigs or dogs. When the dishes are cleared 

 away the Papuan takes his siesta upon the barla, which now 

 serves as a kind of divan. The women on no account use 

 the barla, but take their meals upon the ground. A village 

 consists of several groups of huts (each group having a 

 particular name) which stand around an open clearing, 

 and communicate through narrow paths. The houses do 

 not stand upon piles, ^ and are for the most part small and 

 dark, though well and strongly built ; the roofs in parti- 

 cular, which do not have a flatly-inclined surface, but bulge 

 outside in order that the rain may be the easier carried 

 off. The walls are made either of bamboo or of the 

 stalks of sago-palm leaves. The door is raised generally 

 about half a yard above the ground, to prevent the ingress 

 of dogs and pigs. 



There can generally be distinguished three kinds of 

 huts — those of single people, those of families, and the 

 buambramra, which is usually only used by men, being 

 intended for the youths of the village, and any chance 

 guest. Here will be remarked the baroem, a kind of 

 gong, which plays so important a part in the life of the 

 Papuans. It resembles a thick- sided boat resting upon 

 two trestles, and on the middle of the outer side may be 

 seen a smooth, much-worn patch, the place where it is hit 

 with a very thick stick, by which is produced a dull but 

 loud tone, which has been heard on the coast at as great 

 a distance as five or six miles. All important events, e.^^. 

 the presence of an enemy, a death, or a feast, are by this 

 instrument heralded to the neighbouring villages, the 

 quality of the news being signified by the varying loud- 

 ness of the tones produced, and the length of the pauses 

 between each." 



It is a most extraordinary fact that all the people of the 

 coast here have no means at all of making fire ; wherefore 

 they are obliged always and everywhere to carry a live 

 coal with them, be it either to kindle a fire in a plantation, 

 or, when on a long tour in the mountains, to relight their 

 cigars, which, being wrapped in green leaves, are always 

 going out. On their sea voyages they have generally a 

 live coal at the bottom of the boat, in a broken pot 

 partly filled with earth. Those who remain behind 

 in the villages never forget to look after the fire, and 

 even in the night a small fire is kindled under the sleep- 

 ing-places, which partly makes up for scanty clothing. 

 The warmth penetrates, together with smoke, through 

 the insterstices of the bamboo bedstead, "* so that one- 

 half of the sleeper's body is warmed, in fact roasted, 

 while the other half is frozen. They are often obliged to 

 get up in the night to see after the fire. The mountain 

 people are rtet obliged thus to tend, Mke the pi;iestesses of 

 Vesta, an eternal flame, but understand how to kindle fire 

 anew, and by the following method. A piece of very dry 

 wood, which they term lloi, is split with a stone axe 

 in such a manner that each half is not quite separated 

 from the other. Into the fissure a strong cord, a split liana, 



' The houses of all Malays, whether on the coast or in the mountain«, 

 always are built upon piles sometimes nine or ten feet long. — J. C G. 



* A similar instrument is figured in Schweinfurtb's " Heart of Africa," ac 

 in use by the Niam-Niam tribe. — }■ C. G. 



3 This is probably the equivalent of the bali-bali of the Malays, a frame 

 of split bamboo, raised slightly from the ground.— J. .C. G. 



