164 



POPULAR SCIENCE NEWS. 



[November, 18S9. 



in the eye, as it were, and the previously 

 colored image on the screen appears perfectly 

 white. 



Two more simple illustrations of this prin- 

 ciple are described by Newton in his work on 

 optics, one of which consists in recombining 

 the colors of the spectrum by means of a con- 

 vex lens, which, by concentrating the differ- 

 ently colored rays in a focus, gives a perfectly 



Fig. 2. 



white image. Another experiment is to beat 

 some soap-suds into a foam, when the little 

 ' bubbles of which it is made up will be seen 

 to be brilliantly colored. But when the foam 

 is observed from a distance, the different 

 colors cannot be distinguished by the eye, 

 but are blended together, and the mass 

 appears brilliantly white. 



placed under tlie surface of mercury in a small ves- 

 sel. When the inverted tube has been fastened in a 

 vertical position, the column of mercury will sink 

 about six inches, leaving a transparent space con- 

 taining highly rarefied air in the upper part of the 

 tube. The operation of filling the tube should be 

 performed over a large open vessel, so that in case 

 of an accident the spilled mercury may be saved. 

 As the operation of boiling the mercury in the tube 

 is a rather delicate one, inexperienced experimenters 

 will probably find it sufficient to boil only the first 

 small quantity introduced into the tube, to remove 

 the large bubble of air usually remaining in its 

 pointed end. Great care should be taken not to 

 inhale the deleterious vapor of mercury. 



When the poles of an induction coil, giving a 

 spark about half an inch long, are connected, one to 

 the outer extremity of the platinum wire, and the 

 other to the mercury in the small vessel, the room 

 being darkened, a stream of violet light, divided 

 into luminous sections, will be seen to pour from 

 end to end of the transparent space. 



[Original in The Popular Science A^ews.J 

 A HOME-MADE GEISSLER'S TUBE. 



BY L. BYLLESBY. 



The remarkable beauty of the electric discharge 

 through rarefied gases, may be very well shown in 

 the following simple manner : 



Select a clean, dry, glass tube, about thirty-six 

 inches long, having an inside diameter of one- 

 quarter of an inch. Close one end of this tube in 

 the flame of a Bunsen burner or alcohol lamp, by 

 drawing it out over a piece of platinum wire, so that 

 one end of the wire shall project a short distance 

 into the space inside the tube. 



Care should be taken to make this end strong 

 and absolutely air-tight. The tube must now be 

 filled with mercury. This may be done by attach- 

 ing a funnel to the mouth of the tube by means of a 

 short piece of rubber tubing. The tube is then 

 inclined at an angle of about 30°, and a small quan- 

 tity of mercury is carefully poured in. The tube 

 should now be held in the Bunsen flame till most of 

 the air bubbles have been expelled from the mer- 

 curv by boiling. More mercury is now added and 

 treated in the same manner, and this operation is 

 continued until the tube is filled. The open end of 

 the tube is now tightly closed with the finger and 



THE OPACITY OF GLASS. 

 Some interesting experiments have been under- 

 taken by Herr Herzberg, with the co-operation of 

 Herr G. Schulze, chief engineer of the Berlin works 

 of Messrs. Frederick Seimens & Co. , for the purpose 

 of ascertaining the loss of light in passing through 

 window glass of various kinds in general use. The 

 experiments were conducted with a Bunsen photo- 

 meter, in which two Argand gas burners of equal 

 illuminating power were placed at the two ends of 

 the graduated bar. After equality of illumination 

 of the screen hrd been established, a plate of the 

 glass to be tested was interposed between one of 

 the end lights and the screen, and the extent of the 

 displacement of the latter thus necessitated for the 

 re-establishment of equality of illumination on both 

 sides gave the measure of the opacity of the glass. 

 A simple translucent, but not transparent glass, 

 showed a loss of 27 per cent, of light. Cathedral 

 glass, such as is used in stained glass work as a 

 basis, being clear, but with a slight ground tint, 

 showed a loss of I2?i per cent. Plain cathedral 

 glass, with a white tint, also showed a loss 

 of I2''3 per cent. Plain white Rhenish "double 

 glass" gave a loss of to per cent. Plain thin 

 mirror glass obstructed 10 per cent, of light. 

 The two last together, with an interval of six centi- 

 metres between thein, showed a loss of 21 per cent. 

 Cathedral and Rhenish "double glass" together, 

 with the same interval, showed a loss of 23 per 

 cent. A ground glass with cut stars, together with 

 a white background, such as is found in house fan- 

 lights, obstructed 60 per cent, of light. A new- 

 clean piece of ground glass, without stars, together 

 with the dusty white glass background, as in the 

 preceding experiment, showed a loss of 40 per cent. 



ELECTRICAL NOTES. 



The Result Will Be the Same. — American 

 Notes and Queries has instituted an inquiry among 

 the most eminent scholars of the country to deter- 

 mine the best word to express execution by electri- 

 city. The answers, as far as received, are remark- 

 able for the variety of suggestions. Among them 

 are electrophon, electricize, electrotony, electro- 

 phony, thanelectrize, thanatelectrize, thanatelectri- 

 sis, electromort, electroctony, electroctasy, fulmen, 

 electricide, electropoenize, electrothenese, electrocu- 

 tion, electroed, electrostrike, and finally joltacuss or 

 voltacuss. 



Cooking by Electricity. — The Hotel Bernina, 

 at Samaten, in Switzerland, is situated near a 

 waterfall, which for some time has been utilized to 

 supply light in the hotel. During the long days of 



summer, the light is only required for an insignifi- 

 cant time every day, and the proprietor conceived 

 the idea of employing the force otherwise wasting 

 itself to supply heat for culinary purposes. This 

 has been carried out by a series of resistance wires, 

 which are heated to a red heat by the current, and 

 replace the fires hitherto used, with great comfort 

 and convenience, besides saving the fuel. 



A New B.\ttery. — M. Fortin has recently de- 

 scribed a new bichromate battery constructed as 

 follows : It is made of a number of rectangular cells 

 of 4in. wide by o.yin. deep, placed one above the 

 other. The bottom of each cell is pierced with 

 three holes, in which are fixed small carbon rods, 

 which project slightly above the surface of the cell. 

 The zinc plate which forms the negative elfement 

 rests on these, and itself supports three fragments of 

 india-rubber, which separate it from the positive 

 element — a plate of hard carbon. The inventor 

 states that ten of these cells will drive a glow lamp 

 of 9'a candle-power for ten hours. The exciting 

 fluid is made by dissolving one pound of bichromate 

 of sodium in a gallon of water, to which has been 

 added one pound of commercial sulphuric acid. 



A Narrow Escape. — An accident to one of the 

 employes of the Fort Wayne Jenney Electric-light 

 Company occurred recently at the company's factory, 

 and is interesting as showing the exaggerated nature 

 of many of the statements made with regard to the 

 danger of the alternating current. There is no 

 doubt that in this case the man received the full 

 potential of the machine, as he (believing the ma- 

 chine was not running) deliberately seized two brass 

 couplings connecting the machine to the primary of 

 a converter, in multiple with others, and discon- 

 nected them from the converter. The result was 

 that he received a severe shock, falling forward, and 

 burning his hands somewhat severely; he did not 

 become unconscious, and after a few seconds suc- 

 ceeded in getting free. Beyond the burns on his 

 hands and the shock to the system, he was not much 

 the worse, and expected to be at work again in a 

 day or two. The machine was delivering current at 

 something over 1,000 volts — probably about 1,050. 



A New Standard Galvanic Cell. — M. Gouy 

 has devised a cell which is so simple in construction 

 that it may be used equally well with either gal- 

 vanometers or electrometers. It is composed of 

 zinc and zinc sulphate, with mercury and mercuric 

 oxide. The mercury, which should be previously 

 well purified, is placed in a flask so as to form a 

 layer 2 cm. to 3 cm. in depth. Immersed in it, 

 and sealed into the glass, is a platinum wire, which 

 thus forms the positive pole of the element. Yellow 

 mercuric oxide covers the mercury in the flask, and 

 above this layer is placed a lo-per cent, solution of 

 pure crystallized zinc sulphate having a specific 

 gravity of 1.06. An amalgamated rod of pure zinc 

 is then immersed in the zinc sulphate solution, and 

 forms the negative pole of the cell. The flask need 

 not be closed to the air, unless it is wished that the 

 arrangement should be portable, in which case the 

 neck of the flask is closed, and the zinc rod is placed 

 In a tube partially closed, with some porous mate- 

 rial. After a few days the E. M. F. acquires a 

 constant value of about 1.39 volts, and varies only 

 slightly with the temperature. When the current is 

 not more than o 001 ampere, the polarization of the 

 plates rapidly disappears on breaking the circuit. 



-— *♦> 



The Passivity of Cobalt". — According to Ernest 

 Saint-Edme, the so-called "passive state" of iron 

 and of nickel is merely a chemical property possessed 

 by their nitrides. This state of passivity is con- 

 nected with the degree of affinity of the metal for 

 nitrogen, t. e , in a decreasing order for iron, nickel, 

 and cobalt. 



