82 



SCIENTIFIC NEWS. 



[July 2 7l IS 



Mr. Harcourt subsequently modified this lamp and 

 exhibited it at the Manchester meeting of the British 

 Association before the Physical Section. Instead of 

 burning a mixture of air and pentane, this form of lamp 

 burns pentane vapour only, and burns steadily, although 

 it has no glass chimney round the flame. 



From our illustration, which we owe to the courtesy of 

 the Woodhouse and Rawson Electric Supply Company of 

 Great Britain, it will be seen that the lamp is somewhat 

 like an ordinary spirit-lamp, with a metal chimney above 

 it. 



The chimney is composed of two portions, an upper 

 and a lower one, the latter being doubled so as to main- 

 tain the inner one at a constant temperature. 



On lighting the lamp and placing the chimney in posi- 

 tion the flame rises above the edge of the lower tube, and 

 by suitable adjustment of the wick can be made to enter 

 the upper chimney. In the latter are two slots diametri- 

 cally opposite to each other, and the flame is raised so that 

 its tip lies between the top and the bottom of these 

 slots. 



From experiments it has been learned that variations 

 in the height of the flame do not produce much alteration 

 in the amount of light radiated from its central portions ; 

 so to obtain a light of given candle-power it is only 

 necessary to vary the distance between the upper and 

 lower chimnies. To enable this to be done accurately, 

 small gauges, one of which is shown to the right of the 

 figure, have been made ; one of these is placed on the 

 lower chimney, the upper is lowered upon it, fixed in 

 position by the clamping screws shown on each side 

 of the lower chimney, and the gauge carefully with- 

 drawn. 



After the lamp has been burning for from ten to fifteen 

 minutes there is scarcely any variation in the height of 

 the flame, and consequently the light emitted is for all 

 practical purposes constant. 



The unit in Germany is a paraffin candle, 2 centi- 

 metres in diameter, with a flame 5 centimetres high. A 

 lamp burning "pear oil," or amylacetate, without a wick 

 is being introduced. 



M. Violle has suggested a standard which should 

 please those who are devoted to the French metric 

 system. He proposes to take as a unit of light, the light 

 emitted by one square centimetre of platinum at the 

 point of fusion. Of course a larger quantity of the 

 molten metal is used, and a screen with a hole of an area 

 of one square centimetre is placed before it. A mixture 

 of solid and of liquid platinum behaves like a mixture of 

 ice and water. Although the ice may be melting, yet as 

 long as there is any left, the temperature will be that of 

 freezing point, and conversely if freezing is taking place. 

 The addition or withdrawal of the heat only melts or 

 thaws the ice, and does not alter the temperature of the 

 mixture. This action ensures a constant temperature, 

 and therefore a constant intensity of light, for the sur- 

 face of the molten metal would be the same under all 

 ordinary conditions. The original experiments were made 

 with an oxy-hydrogen furnace of elaborate construc- 

 tion. Recent experiments, according to a paper by Mr. 

 Dibdin, lately read before the Society of Chemical 

 Industry, have been made with a thin sheet of 

 platinum foil, with a screen in front, having a hole 

 of a definite size, and a blowpipe behind, by means 

 of which the temperature is raised until the metal melts, 

 and a hole is pierced in the foil. The light, which was 

 being continuously measured while it increased in 



strength, is considered to be of a standard intensity at 

 the moment of the highest measurement, just before the 

 foil melts. It is said that this gives more reliable and 

 uniform results than might be expected. The foil- is 

 rolled off from one reel to another, so that the operation 

 can be repeated with ease. 



There are several important considerations as to the 

 colour of the light which is to be measured, and its rela- 

 tion to the colour of the standard ; for example, it is a 

 matter of individual judgment rather than a matter of 

 measurement to compare the light of a candle with that 

 of an electric arc lamp. These considerations and the 

 means of making the comparisons and measurements 

 must be left for another occasion. 



It is not, however, merely light which we want, but 

 illumination. A badly arranged system of electric arc 

 lights may give a considerable amount of light, but the 

 illumination produced may be very bad. The 

 amount of light required to illuminate a room is very 

 difficult to calculate, since it depends not only 

 on the superficial area of the floor, but on 

 the reflecting power of the walls, and this is dependent 

 on their colour and height. One authority gives 20 

 candles to 40 cubic yards of space, but it is impossible 

 to apply such a formula to ordinary interior lighting. 

 Out-door lighting is more easily reduced to rule, for 

 there is but little assistance to be gained from reflection. 

 For such cases Mr. Preece has suggested as a standard of 

 illumination the illumination produced by a "bee Carcel" 

 at the distance of a metre, which is equivalent to a 

 " parliamentary candle " at 127 inches. The illumina- 

 tion at the foot of an ordinary lamp post is about one- 

 tenth, and that of the full moon, on a clear night, is 

 about one-thirtieth of this unit. 



A New Cigarette Machine. — Messrs. Jadowsky and 

 Schmitt have, after a long series of trials, perfected 

 a machine for the manufacture of cigarettes, which is 

 remarkable for its ingenuity and workmanship. The frame 

 of the machine consists of a cast-iron table, supported on 

 angle iron legs, and the various organs of the mechanism are 

 geared to a main spindle, which receives motion either from 

 a hand crank or by power from a belt. At each revolution 

 of the spindle a complete cigarette with cardboard mouth- 

 piece is turned out. The tobacco, slightly moistened, is 

 placed in an open trough, the bottom of which is in part formed 

 by an endless cotton band travelling forward under a knife, 

 which automatically cuts off the quantity of tobacco required 

 for one cigarette. This quantity is then pressed into a cylin- 

 drical form between a pair of semi-circular metal sleeves, and 

 retained in this mould until a little piston pushes it into the 

 paper envelope, which has, meantime, been prepared by 

 another part of the machine. The tissue paper and the tape of 

 cardboard for the mouthpiece are on separate rollers under 

 the table, and the former is drawn between guide rollers under 

 a printing roller, which prints the brand on to the paper. The 

 paper band is then seized by a gripper, whilst a knife cuts off 

 the length required to go round the cigarette, leaving sufficient 

 length for the lap, which is gummed by being pressed against 

 a roller. The piece of paper is next coiled over a mandrel, 

 and then released from the gripper, which moves back to 

 seize again the end of the paper tape, whilst the paper cylin- 

 der is pushed into a metal tube. Meanwhile the cardboard 

 tape has undergone a similar operation, and a little cylinder 

 of cardboard is pushed into the tube from the other end, where, 

 through its own elastic expansion, it jambs itself tight into the 

 tube of tissue paper. This receives now its charge of tobacco 

 from the mould already mentioned, and the finished cigarette 

 is thrown on to a travelling band, which deposits it in a box 

 at the side of the table. — Industries. 



